I had this bug a few days ago (I assume it is one).
Normally when you place a packed building with mongols and i.e. a villager enters the placement zone the building does not get placed and the villager continues.
In my game more and more villager and traders tried to pass the area going back and forth for a few steps then try again, but the building would not cancel to place itsself and therefore blocked the way. Took a minute or so till I realized.
I typically have the opposite problem. I move a Ger into a better position, then check back minutes later to see that it never unpacked due to villagers constantly walking over its footprint. Much villager time spent walking in the meantime. I wish buildings would be more persistent about unpacking themselves than they are.
hm in my case neither the building stopped unpacking nor did the villagers walk through it and continued their work. Since they do not count as idle (they still had the order to mine gold) it is tough to recognize in a hectic game.