Are they killing the boss? And I want to see the props gump for the mini spawner to see if the spawn is actually active or not when this is happening. The props may not be invalidating right, so the mouse over of the spawner may be misleading.
ohh, no he must be killed because the spawn gets advanced to that point. Just no respawn. In the past spawn also did lag out sometimes and it would only have run half way but lately it has just been the bosses. They get killed, just in rare situations do not respawn.