I enjoy sniping whilst eating my dinner, so used the rock in solo last night. Was definitely broken. My way round it was to leave one minor enemy up in the field below, pop down and kill that last one, then the next wave spawns properly. If you clear all enemies from the rock you most assuredly have to keep going to the door to restart wave one. I understand everyone plays differently. My issue is with developers trying to change people's playing style. Snipers are in the game for a reason. There shouldn't be dead zones on an open map.