This is kind of an edge case, but I'll log it anyway.

While spectating, if the active vessel stages early such that, for example, the capsule is separated from the booster but the booster is still in contact and thrusting, there is a high likelihood that the spectator's vessel will explode. The spectator will get the vessel reset at the next full update, but then nearly every other full update will have another explosion.

Example of the spectator's view:
http://imgur.com/sB2pJaE
The active player had stage early while the service module was at full thrust. The spectator saw the capsule bouncing around about 1m in front of the service module, while the active player had the capsule still in contact with the service module as you would expect. The instant of staging, the spectator's vessels exploded, then reset, then exploded again, as described above.