With certain items, like potions for example, I get "Item transfer error" and underneath that "There is no room for this item" when I right click on them. Otherwise my game seems to be working normally. I can still use the items without issue. Is this something I should be worried about or just a minor glitch?

Latest CO8 and Temple+ installed.

Do you mean it happens when the looting/shop UI is open? Otherwise right clicking them is meaningless, you can't equip them.

del

Yes, it also happens in the loot/shop window. It's not a big deal as I can still loot/shop by left-clicking and dragging the item. I was just unsure if it's something I need to worry about.

Another clarification, since I can't reproduce the error:
Does it occur when you try to buy/loot from, or when trying to sell /put item in?
If the former, can you send me a save demonstrating the problem? You can use a file sharing site like wikisend.com.
If the latter, then right click is interpreted as trying to equip the item, which is not possible for potions. You can alt+click to sell/transfer.

Right click doesn't do anything for me in the barter window. I have to left click and drag to purchase something.

When looting a corpse, it moves whatever I right click to my inventory.


Another oddity I noticed is that there are no slings in my game. Or at least I haven't come across one yet. There are plenty of bullets, but I can't find a sling to use them. Do you know if the loot at merchants is random? Shouldn't at least one of the traders in Hommlet have a sling?

I think the leather worker might sell them.

Yes, the leatherworker has a sling. And Bing has a good chance of selling a masterwork one if you heal him.

Hever seen him not having one for sale

Sadly slings in this game are just throwaways.