This is an issue I've been having for a couple of months, and other people have encountered it too.
Basically, after working for one game, every single prop in the map that was affected by a prop mover will break entirely. The bugs these pieces have had that I have identified are these, so far:
Visual location of the prop usually rotated to one of its edges and always with the prop's default orientation.
Prop becomes indestructible to any damage.
Prop stops reacting to any other device that is modifying it. (Including the prop mover)
Some extra observations I've made is that those things only happen once the prop mover is enabled, as seen in this video: