Most of the time it's because the Move Route causes the event to collide with an object, preventing it from continuing. With Wait for Completion checked then the event will just hang, waiting for a completion that will never happen. Try enabling Through on the event and see if it moves to the correct place, then correct the move route accordingly.
Usually the most troubling places are invisible events. Even though they're placed above or below the player, allowing them to pass through it, events will still get stuck on it unless Through is enabled.