That almost falls in line with another bug I reported on roads being upgraded being slower than dirt roads. It seems that a building being moved or upgraded might be unable to impart its effects on other npcs. For the road being upgraded, it didn’t give the npc faster walking than on plain ground anymore and was thus slower than the dirt road. In your case, it seems the building is no longer seen as a target by hostiles while it is in limbo. There needs to be more granular state checking on anything in a transitory state.