Hi Daniel, thank you for the response. My Catalina partition is on my internal SSD, using “APFS Volume • APFS” (factory settings) and a GUID partition map.
However if this is a hard drive issue, I save all my projects directly onto my NAS DS218j system (wirelessly). Maybe there is some interaction with that and Dorico 3 specifically because I’ve done 100+ Dorico 2 projects the same way without this issue, which appeared immediately with Dorico 3.
I’ll try saving to the internal SSD first from now on and see if the files corrupt again. I’d like to keep using Dorico 3 because the lyric pasting feature saves me so much time.