Save file gets corrupted and merges with an older one somehow

Mentioned this in another thread, but thought I’d post my own too.
I have a quicksave right before I take the last shot on a base defence mission (yep I’m save scum). once the enemy is killed the geoscape loads to an older completely different game point entirely. I.E it is:

  • a completely different map position(and ship) on a scavenge mission, not the current base defense mission.
  • the ship I was using no longer exists (not acquired yet)
  • The soldier that takes the last shot, is gone (not acquired yet either)

The files are mixed somehow.I have previously turned cloud saves off. I am using the Epic platform, Win 10 (20H2).