Despite how wonky and unfinished it is, I have a lot of fun with Ultima 8 back in the day. Nonetheless, there are a number of problems with it that I found glaring even back then, all of which feel like they should be easily fixable, but frustratingly were never addressed. Most have to do with the spellcasting system, but there's other stuff there too.

I find it odd that these very obvious issues hardly seem to get talked about....

Bonecrusher doesn't do what it says on the tin
Problem: In the initial release of Ultima 8, the game included a weapon called the Hammer of Strength - it's often the first magic weapon you'll find. After the patch, it was changed to Bonecrusher - named after a legendary hammer found in one of the books. The problem is that in the book, Bonecrusher is used to destroy legions of skeletons. But this hammer is utterly useless against them, since Skeletons killed with it will keep resurrecting endlessly anyway! Not much of a Skeleton-killer if it can't even kill Skeletons for good.
Solution: Enable the hammer to kill Skeletons permamently. There are at least 2 effects that do that: fire damage (as per Sorcery spells and Daemon attacks) and the Grant Peace effect (from the Grant Peace spell and the Slayer mace).

Summoned creatures will murder you
Problem: If you use Summon Skeleton (Necromancy), Summon Monster (Thaumaturgy) or Create Golem and order it to attack an enemy (Necromancy), the creature will turn hostile on YOU after it kills its enemy. This makes these spells useless, since if they managed to kill the enemy, they were obviously stronger than the enemy they just killed, leaving you with a bigger problem. The issue is only made more frustrating by the fact that Summon Daemon - which lore-wise should be the most risky summon - is actually the only safe summon to use, since the Daemon will disappear after completing its task.
Solution: Two possibilities. Either set the monster AI to neutral after it kills its target (the same effect as a Confusion Blast (Thaumaturgy) spell has) or make the monster disappear after it completes its mission (as per Summon Daemon).

Summon Monster leaves permanent corpses
Problem: No idea why, but any monster summoned by Summon Monster leaves behind a permanent corpse. Even if you leave the area and come back they'll still be there. The only way to get rid of it is to dump it in deep water/lava.
Solution: Just make it treat the monster the same way that Summon Skeleton does, I guess? Those don't ;eave permanent corpses as far as I know...

Targeting is inconsistent and wonky
Problem: Some spells will pause the game and let you target enemies (eg, Grant Peace). Other spells will not and require you to target a moving enemy (eg, all Sorcery projectile spells). This makes some spells super-hard to aim.
Solution: Ensure the same pausing mechanic is used for every targeted spell. Or if not, ensure no spells pause for targeting. I'd prefer the former. It might also make Sorcery attacks spells marginally better (they are almost useless as-is).

Call Quake has no practical applications
Problem: The Call Quake spell (Necromancy) does nothing remotely useful. It will make you and some of the monsters fall over if theyr'e standing still, that's it. Not very useful as monsters will usually be moving unless they're already attacking you. And if they do fall over, their animation for getting up is much faster than yours, so you'll be at an automatic disadvantage. The spell does no damage to enemies.
Solution: Allow the spell damage all enemies in the area. Perhaps in caves, it can cause stalagtites to fall on enemies while they are in caves for added damage?

Call Destruction leaves permanent graphical effects in the world if interrupted
Problem: If you cast Call Destruction (Thaumaturgy) and are interrupted for any reason (eg, attacked by an enemy) then any effects that were in-progress on the screen (eg, lightning bolts, explosions) will freeze and stay forever - even if you leave the area.
Solution: Make this not happen. It's the only spells where effects freeze in this way, it's obviously missing some sort of cleanup routine that other spells do have.

Thaumaturgy spellbooks never run out of charges
Problem: With the notable exception of Confusion Blast (the very first Thaumaturgy spel you learn), all Thaumaturgy spellbooks, once 'charged', can be used infinitely. Some, such as Meteor shower, can just be double clicked many times to stack its effects until the screen is a deadly rain of fire. Confusion Blast however will de-charge the spellbook after one use.
Solution: I'm almost certain the spellbooks were meant to have only limited charges (possibly just 1, like Confusion blast) - having infinite charges makes them insanely overpowered. As such, apply the same logic as Confusion Blast to the other spellbooks too.

The Scroll of Dispelling Magical Portals never runs out of charges
Problem: The Scroll of Dispelling Maigcal Portals can be used infinitely, even though Mythran tells you it will disappear after use. This also means it acts differently from all other scrolls in the game.
Solution: Either edit Mythran's text so he doesn't say it's good for one use only, or make it good for one use only (though this would be annoying since it's not always obvious where it should be used)

And that's just what I consider the major bugs/internal inconsistencies. Anyone got any more?

Ultima 8 will always have a special place in my heart, and I still play it from time to time, but yeah, it's a broken mess.

Apart from the problems you mentioned:

- There's no use to get any other magic weapon than The Deceiver, which is easy to get if you know where to look.
I get the feeling that their special abilities are for the most part non-functional. Take the Slayer: 10% chance to kill an enemy outright. I have never had enemies die after one hit. The thunderclap usually comes knocking when I've beaten an enemy repeatedly over the head, e.g. I get the feeling this weapon's special only sets off when an enemy is already about to die from a hit.

- Even with your stats maxed and with a good magic weapon it takes way too much time to kill a simple ghoul...

- ...and you can max some of your stats right at the start of the game, by repeatedly attacking the first guy you meet.

- Flasks of oil, death disks, those gems, they're all useless. There isn't any nice loot in the game, except for magic armour and a select few magic weapons.

- Chests are for the most part empty.

- Chests are ALWAYS trapped! Always. It's ludicrous.

- The magic armour that can be gotten by going through a side quest is incredibly hard to get. Chances are that by the time you get it (if at all) you'll already have another magic armour, and the other magic armours you can get actually have a better armour rating than the hard-to-get one.

- The spell system is frustrating as hell, with the exception of Theurgy.
Sorcery spells being the worst. It takes such a ridiculous amount of time and effort to fill a focus with a sorcery spell.
The whole system is incredibly clunky.

- No party members, no bows; Just a huge step back from U7.

- Everything looks so gray and boring. The catacombs, caves, they look the same everywhere.

I doubt anyone will ever be able to fix these problems though. It's pretty clear that Origin did not get the time required from EA to finish this game. It's somewhat functional, but it feels like a beta, or alpha even.
Heck, you couldn't even jump to specific spots when the first version came out; platforming segments were ridiculous. I am probably one of the few people on this planet that finished the game in that state. Let me tell you, it was hell. I wouldn't have the patience for it nowadays.
They didn't even come close to finishing it. It'd be easier to just make a new Ultima 8 from scratch.

I will always love this game, for nostalgia's sake, but I think any new player should steer very clear of this mess.

Some problems would be solved simply by removing creature respawns to begin with. Make enough Grant Peace to wipe out every skeleton and enjoy exploration without further interruption! As it is, it's simply not worth going through any location more than once because anything you "kill" or dispose of (tossing defeated skeletons into water to prevent respawn) is completely undone. I usually end up running speedrun-style through revisited areas because it's just too tedious to fight everything again and again. While U9 also has respawns outdoors, at least the dungeons don't respawn (as long as you're careful to remove the same bone from each skeleton you kill so they can't reform). Maybe the devs were also tired of U8's dungeon respawns.

As for glitches, losing items because they bounce out of view behind a wall is always super frustrating. This is made worse by GoG's removal of or interference with the cheat menu so you can't use it to remove wall segments to reacquire the lost item(s). EDIT: cheats still work via save-game editing (avatar.dat npcdata.dat or the save files themselves) but the F7 key doesn't as it was reassigned by the last official U8 patch (use F9 instead).

Then there are the Necromancers, three of which don't need the plot-intended spell for communication. Oops.

I was also disappointed by the Slayer weapon; figured from the description it might keep skeletons down but alas, useless.

Thankfully the final patch removed many of the arcade elements, but it's still far too easy to fall to your death. Saving regularly is a must.

I agree with some things, though a lot of the above aren't actually bugs, just crappy/rushed design.

However, I don't entirely agree with everything. For example:

- Slayer definitely works as intended. I've insta-killed trolls with it long before the weapon would have killed them from damage alone. It's crappy against weak enemies but it's good against HP sponges.
- I actually really LIKE the magic system, though not the bugs. The need to perform rituals and prep for the casting is actually a great touch. The real problem is that certain spells are nigh-useless (eg, most of the Sorcery attack spells), especially when compared to other options you have at that point. If they had some utility to go with the effort of preparing them it would be different.

Any ever try reviving the Pentagram engine? Seems like it'd be the easiest way to address all of these points. I liked U8 a lot for the story/themes/worldbuilding and getting to revisit that without the janky bits would be lovely.

For that matter are there any Exult mods to de-EAify Serpent Isle? I seem to recall that also getting hit with a bunch of unfinished bits because EA rushed it :T

I never had the same experience with the Slayer, but I'll take your word for it. :)

About the magic system, don't get me wrong, I love the idea as well. Putting down all the ingredients and candles in a pentagram, binding a little of Pyros' power into a single item. It's incredibly original.
The problem is: Ultima 8 is notoriously bad when it comes to interacting with items in the game world.
Even though the patch made it slightly easier to create fire spells, it is still very time consuming and too often I end up with trying to move an item into the right spot while also walking around, getting in my own way or standing on items that I was trying to move.

I don't blame Origin for it, because I am sure they would have fixed it if EA gave them the time they needed (seriously, I loathe EA 'til this day). They could probably have implemented a system where candles and ingredients would simply snap into place on the pentagram.

When it comes to Earth magic, my only beef with it is that every spell you create only has one charge.
I can't remember, but I think any extra stacks of ingredients in the bag would not lead to more spells. It'd simply destroy the extra items you put in there, giving you one spell in return.
So creating a number of spells ends up with the player needing to drag ingredients into their bag one by one, making the spell, dragging more ingredients, making the spell... over and over again. There's one mod floating around that at least fixes Cantra from not being cureable (Serpent Isle Fixes), but other than that, nothing.
I read somewhere (a long time ago) that the developers had the idea to have the player undo the damage caused by the three banes, restoring the cities to their former glory, but yeah, no time, so we're stuck with three nearly empty cities and a huge pile of bodies.
I'm not sure, but I figured they just let almost everyone die after the bane events so they wouldn't have to write any new dialogue, for which they had no time.

So going from this:

http://exult.sourceforge.net/forum/read.php?f=1&i=9870&t=9814

It sounds like the original idea was to have everyone "corrupted" instead of dead, and the issues were getting that the usecode scripting working for that, and not the dialogue. It doesn't sound like you could ever restore the towns though?

[url=https://tcrf.net/Proto:Ultima_VII_Part_Two:_Serpent_Isle]https://tcrf.net/Proto:Ultima_VII_Part_Two:_Serpent_Isle[/url] also refers to a prototype version so I wonder if anything interesting could be yoinked from that and cleaned up.

Re pentagram, is there more information available anywhere other than the file format readmes that come with Pentagram itself?

Nope. Yeah, 99% is utterly useless. And it's easier to just ignore enemies altogether. They're all terribly slow.
In fact, I don't think you ever need to kill anything through combat or spell-casting. I think you might need one banish daemon spell at some point (memory's hazy), but even the two daemons Malchir sends after you can just be avoided by running past them. Hmm, that's not so bad then. Not as user friendly as Air, but at least not even close to being as time-consuming as Fire. You should absolutely finish it. Even though the game's not as open as The Black Gate, it's rather linear, but it's quite the adventure.
Your objective might be a bit unclear at some points; there are some instances where you need to ask the right questions to the right people in order to progress the story line, so I wouldn't be ashamed of myself to use a guide.

Is there any way to fix busted save files? I've got one about halfway through the game that keeps crashing. I *really* don't want to start over at this point and I don't even trust that starting over again would work. I've found two parts that will freeze my game. One is trying to walk through Mordea's room when she's asleep, and another is giving the dagger back to Lothien and trying to complete the ritual. I'm guessing there's a specific animation or something that's causing the freeze. I'm also getting weird artifacts on the ground that will randomly flash to the wrong texture, like grass that occasionally looks like stone, for example.

I have no idea how to fix busted save files, but I have several savegames for DOSbox. I've attached a zip file here. There are 4 directories there, each with savegames saved at different points of the game. Maybe you could restore at a point that is similar to a place in the game you were before?

EDIT: hmm, I guess I can only attach jpg files. Here is a temporary link that will expire in a month: https://easyupload.io/xrb50c