I’ve only seen this happen under 3 circumstances.
1 - The movie is unmatched
2 - movie matched manually using fix incorrect match then the file itself was changed (filename, property, etc)
3 - You are using a custom agent which is causing the problem
Do either of these describe your situation? If not, can you provide the xml for one of these movies and I’ll see if I can reproduce.
I’ve personally not had any of my custom edits change randomly on me.