Rally point crash

I have a certain building that can train units, research upgrades, upgrades to another building.
When I try to set its rally point to itself or to another building, the game crashes. I have no triggers that detect setting rally points...

Further testing:
I removed every single trigger from the map, it still crashes.
Normally the building is upgradeable from another building which does not train units, and if I place this building on the map from start and try to set a rally point, it doesn't crash.

So far I made a workaround that detects when the unit finished upgrading, removes it and places a new one.