If you don’t rename/delete that folder between Proton version changes, files relating to both versions will combine, which can sometimes cause it to not run as it should. Local save games might be stored in there as well, so don’t delete the folder before making sure your progress hasn’t been lost (it’s also in Steam Cloud but sometimes deleting local save games can result in sync problems).
I’ve played for 80 hours and haven’t had any problems when using Proton Experimental.
If you switch proton versions, rename the numbered folder for Helldivers 2 (553850) to force Steam to create a new folder for it.
It should be in your Steam Library at /steamapps/compatdata/553850 (where your Steam Library folder is will vary, so I can’t give a specific path)
If you still have trouble, look through people’s reports on ProtonDB for things you can try. https://www.protondb.com/app/553850
If you don’t rename/delete that folder between Proton version changes, files relating to both versions will combine, which can sometimes cause it to not run as it should. Local save games might be stored in there as well, so don’t delete the folder before making sure your progress hasn’t been lost (it’s also in Steam Cloud but sometimes deleting local save games can result in sync problems).
Thanks for that info. I tried a lot of the suggestions on protondb with no effect. If I re-purchase it I’ll try the folder renaming thing.