From the Paradox Forum:

"Thank you for playing BATTLETECH! We appreciate your patience and support as our team works to quickly investigate and address reported issues with the game. Release 1.0.4 is now available for users on Steam and GoG. Note that the public_beta branch is still on Release 1.0.3 plus the additional Beta Launcher for BATTLETECH - we will also be advancing public_beta to contain 1.0.4 plus Launcher later this week.

If you experience any issues after updating, the first step we recommend is to restart your computer, and then verify integrity of game files. Occasionally, the Steam update process can act weird - this will ensure that the update has been properly applied.

Players with nVidia graphics cards should now update to the latest nVidia driver and not use the BT game ready driver that was released at launch.

As always, if you experience further issues please contact Customer Support at: https://support.paradoxplaza.com

Release 1.0.4 Notes, 5/21/2018
Fixed an issue introduced in Release 1.0.3 where the campaign timeline could stop advancing under certain circumstances - most commonly, after the death of one or more MechWarriors with active temporary tags (e.g High Spirits) on them.
Additional note for players who mod various game files…Reminder that modding is not officially supported. If you have saved a game with any mod active, that saved game will not work after an update has been applied unless you replace all modded files exactly as they were when the save game file was created. Saved games require the exact same data state in order to function properly."
HBS_Comanche, Today at 01:00

Those "temporary tags" are powerful!

I`m going to wait a couple of months or until patch 2.0...

...then it might be acceptable.

If you are on 103 and you play the campaign, then I'd seriously recommend using this 104 patch.

Just had my first major bug since release, no clue if lucky until now or a 1.0.4 issue.
Was in combat and on the 5th turn the second mech I moved got stuck on shoulder cam and then stayed like that with no UI or keyboard controls working, except escape for the game menu.
Got to love the autosaves making time loss for such a thing into mere minutes.

With that one autosave bug that we had (reportedly fixed), I've made it a policy never to use that feature. I always manually save before each mish, to protect from strange things happening.

I do tend to save quite a bit on my own but somehow this time I hadn't for an hour or two so was quite the lucky break for once.

1.0.4 increased my load times significantly!

So I am not alone.

1.0.3 Loadtime for my savegames ~27 secs.
1.0.4 Loadtime for my savegames ~51 secs.

1.0.4 nearly doubled the loadtimes for me.