FL. (I've read that ormally that's the problem) I always make a lot of backups because of this, and tried to work on the last backup that didn't malfunction. Even without adding new plugins after a vew backups ...
FL and this still happens. At first I thought I had a bad drive but it's only extremely slow in FL. Tested with Samsung magician and everything is fine.
I have heard of SSDs not being as fast at first ...