One more piece of the SetButtonStart Issue puzzle. I set the SET button to OFF, but ML would still start when I pressed SET while starting the camera. I discovered that I had the camera set to Auto ISO and this would automatically return the SET button setting to ISO and so disable ML wouldn't work. When I set the camera to a specific ISO and then turned the SET button to OFF, I was now able to disable ML on starting the camera. This could explain the sporadic nature of this issue.