I'm dealing with this issue as well. I didn't see this thread and have been posting in another Aerosmith thread as well as one that I started. So I've spoken with Stern tech support a few times as well as emailed with John Borg. They have sent me a Shaft Head (part no. 530-5511-01) and I installed the piece. As I was taking apart the mech I noticed there wasn't a spring that was in the diagram. John Borg himself emailed me saying that spring was deleted as it was not needed (part no. 266-5020-00).
The shaft head did not solve the issue. So I call Stern tech support again and they are now sending me that spring as well as an SD card with the latest software, which is currently installed on my game. They think the software on there now might be corrupt.
I purchased the game new in box from The Pinball Company out of Columbia, MO less than 30 days ago. I've been in constant communication with them as well as Stern to resolve the issue. At this point it is a paperweight in my game room.