Unrelated to that, I think I've found a bug: every once in a while, the process stops, complains about low device storage and I have to push "retry" - after which it keeps going. It seems like the app doesn't clear its temporary files until it fails due to low storage. I can see the app's size growing and growing to over 50GB - which at the moment is all the free space I have - and then, when it hits the wall, suddenly shrink back to 144MB. The largest single file in the Camera folder is 17GB. Then I have to open the app manually and tell it to retry. This means I have to babysit it and can't have it back up everything overnight.
Edit: app version is: Proton Drive 2.3.1. Phone is Samsung Galaxy S22+, OneUI 6.0, Android 15
Another edit: I am now seeing this happen while the app should be idle! Its storage usage just keeps climbing and climbing.