Do you have MangoHud installed? Last week I couldn’t run any proton game on my system until I uninstalled it/ removed the MANGOHUD=1 variable haven’t had this problem before, but something broke. Proton and wine were stuck at launching, no error messages/ logs, etc. drove me nuts.
So I set up my system with btrfs in the last days and I converted two external drives (from ext4) (mainly game) and run defrag and balance, because it was mentioned in a guide to compress the existing files. Was that a bad idea? Didn’t read anything about duplicates.