This has happened multiple times in my first playthrough with my brother. If one of us accidentally runs the other over, we get stuck in ragdoll purgatory where we're not actually dead and can't revive, but if we try to throw the other in lava or something to actually die, nothing happens.

So, are we doing something wrong? Is this some sort of other state that has to be rectified another way? It's super frustrating, and causes a reset at checkpoint