There is a milled slot in the top bracket. It probably just chewed the slot and left the impression it created the slot.I finally installed my mounts today, I cut down my CS top dowels to approximately 5mm and they seemed to good with no binding. Upon removing the driver side mount I find that it is separated and oil is coming out of it. Upon discovering this the top dowel chewed the aluminum bracket and made a channel towards the engine. I Find it interesting find that it would chew it when the mount was broken I didn't have a clue it was broken and there was no oil anywhere around until i moved it from the bay.