I know that if the pto switch is on, the starter will not turn the motor over to start. That is a safety, that is built into the unit. The pto switch is wired into the clutch pedal switch, which in turn goes to the starter solenoid . As far as the pto not turning off, That is a new one to me. Usually, they won't engage, which is usually a wiring issue. I suppose, a switch could go bad, but haven't seen that to often. Maybe, you'll get lucky with a new switch, but I have my doubts. I'll have to check the wiring diagram, as I have not had many issues, of this kind, locally.