Haunted weapons

I recently had the opportunity to rush a nebelwerfer unit just outside its base. My T90 decrewed the weapon smartly. I retreated from the base defenses without being able to destroy the weapon. As I did so I watched the unmanned weapon slowly creep back into the base compound. When next I returned to the area there was the uncrewed nebelwerfer  sitting next to the T2 building. Poltergeists? ???

It happens when a foot-towed weapon (neb or at gun) crew gets killed while they "set/pack up" (you see the little bar above their head) without "committing suicide", while they have a move order.