See right click on Zapper in Steam and go to "Manage->Browse Local Files," open the "Launcher" folder, and right click "generic_bg.mp4" and move it to trash. A community page (https://steamcommunity.com/sharedfiles/filedetails/?id=3263012182) suggested this fix for the steam deck so I did it for me as well.

I am not sure if deleteing the file is needed. I could have tried some other versions of proton before deleting it, or maybe it is required, but the community post said to do it for steam deck so I figured I would try it as well (I am running Linux Mint)