My is currently unable to give a replay, but I'll desribe the bug in detail:
-One more thing, it turns out he was playing in single player mode and did cheats..
You still need to fix this though:
Using a spell that creates a golden portal that can teleport units to a range of ~2000, he sent a unit that has an inventory to the spell selection area.
That unit was then stuck.
I think this is a serious issue because it can cause the loss of a hero