I've noticed while trying to set up parking areas that excavators of any size (other than mega, haven't got those yet) won't travel to parking spots when idle, filtered or not. It attempts to but then instantly drops the task and goes back to idle even though it doesn't have any new orders. I first thought it was because there was still designations in the tower area even though they were completed. Even after removing those they still wouldn't park so it's not the cause.