Oops!
I've had this problem. Bandit fixed under warranty with a new motor that has a larger shaft in it. They still want the retainer plate on the machine but they have told me the larger motor shaft is the proper solution. The retainer plate's purpose is to keep the wheel from coming out of the machine. My Bandit rep told me that it has been tested by the engineers at Bandit many many times to be sure the wheel can't come out and it has never failed. The original motor shaft I'm told worked on paper but in reality a larger diameter one was needed. They did a nice job for me, when the problem came up they sent a new motor and retaining plate to my dealer and they installed same day. I believe, it has been a couple years or so but Bandit sent out notification to all dealers at the time about this could happen.