thx for the info. But it is appearing also without moving warbands. So I guess it is not caused by pathing. My settlement population has crossed 150 ppl, could this cause lag or crashes?
If it's the same world from your bug report, there don't seem to be any stuck warbands, just run-of-the-mill poor optimization.
The longer world updates take, the more chance of encountering an edge case that crashes the game. So the bigger worlds get, the more likely a crash will happen.