It may be a bug in the Release candidate, or just a fluke as you theorized. I’d test it out a few times by closing and re-opening a few different files a few times each in random order. If it happens with all of them and is persistent, consider reporting it as a potential bug and letting Blender’s people figure it out (unless you’re a good enough coder to hunt that succer down yourself in which case… Blender is open source)