https://bugs.winehq.org/show_bug.cgi?id=42394
--- Comment #2 from Matteo Bruni matteo.mystral@gmail.com --- A few days ago we did some troubleshooting in #winehackers on a user's crash with UO + UO Assist. I don't know if your issue is the same but it's probably worth a try.
In the other case, the issue was about the game process running out of addressing space. We found that setting the Large Address Aware flag on the game .exe is a workaround. There are various tools on the internet which can be used to do that (e.g. I found https://www.techpowerup.com/forums/threads/large-address-aware.112556/ with a quick search).
Can you try and see if that makes any difference? If that's not the case, please attach the whole terminal output.