What mode was the server running?
I might've found the issue for one of the crashes, but the other 3 all aren't really tenable to figure out without a consistent reproduction method and/or debugger due to the size of the function.
V1.9.3.1 Update
NOTE: This is a hotfix for the recent V1.9.3 release. Please see that changelog for details.
Gameplay
Fix: Removed a few FA-only hilts that were accidentally added to Open mode.
Models
Fix: Corrected invisible part on Panaka's model.
Full Authentic
Change...
V1.9.3 Update
Gameplay
Change / Fix: Anti-Teamkill System
The TK spec threshold now adjusts dynamically per player based on their score. The baseline threshold on joining is what the cvar is set to minus 100. The difference can be made up for by positive score (enemy kills, doing objective)...
You have to run natively on Linux otherwise you will get kicked from servers by the AC system. So this isn't a very helpful guide.
Someone wrote a native Linux Steam Deck guide here: Movie Battles II Steam Deck installation
If you followed the linux install guide it doesn't talk about downloading OpenJK separately, so I'm not sure exactly what you followed.
I know of at least one case where someone successfully got it working on a steam deck but they did not write a guide.
Please re-download the launcher installer (make sure the file size is different to the first MSI you installed to ensure you have the updated version): https://update.moviebattles.org/launcher/MBII_Launcher_Setup.msi
Update your installation with the new installer and try again.
Well it's always been a little jank, though I'm not even sure it's intended to consistently do a ton of damage when hitting walls. Not a part of the code I plan to dive into either way.
I'm going to go with the latter option for this issue since I don't think it particularly will have a balance...