For over a year now, we have been experiencing an intermittent problem of our B21 quitting. Today I was moving forward slowly when it quit on me. When I try to restart, the fuel solenoid does not engage, audible click. This happened to me 3 times within the first hour of using it, after that it ran without a problem for 2-3 hours, turned on/off whenever I needed, never quit. We have been told it could be one of many things, Ignition switch, fuel solenoid, safety relays for PTO, Clutch, Seat, forward/reverse, etc. With it being intermittent like it has, what is your recommendation for troubleshooting?