According to the PostEditMove() signature, which is declared in AActor class
virtual void PostEditMove
(
bool bFinished
)
it’s not supposed to notify which property was changed (or which widget was moved) and I think the problem of is that he wants to fire a time consuming procedure when the special property has changed.
By the way, I’m experiencing the same problem with NULL pointer. I have UE4.7.2 built from sources.