Problem solved!
Turned out to be a simple wiring issue. The wire from the starter solenoid to the starter switch was the culprit.
I poked and prodded with a test light for a while feeling like I was chasing my tail. Sometimes voltage was present, sometimes not. I finally figured out the problem was right at the starter. There is a ring terminal where the wire connects to the starter and the connection there was faulty. The slightest movement of the wire caused the connection to fail. I cut off the ring terminal and connected the bare wire and everything worked fine. I'll get a new terminal for it soon, but in the mean time she's up and running again.
I guess the timing of the issue had me thinking that this was related to the PTO. Turns out it was just a coincidence after all.
Thanks to everyone for all the replies. Your help is much appreciated.
Turned out to be a simple wiring issue. The wire from the starter solenoid to the starter switch was the culprit.
I poked and prodded with a test light for a while feeling like I was chasing my tail. Sometimes voltage was present, sometimes not. I finally figured out the problem was right at the starter. There is a ring terminal where the wire connects to the starter and the connection there was faulty. The slightest movement of the wire caused the connection to fail. I cut off the ring terminal and connected the bare wire and everything worked fine. I'll get a new terminal for it soon, but in the mean time she's up and running again.
I guess the timing of the issue had me thinking that this was related to the PTO. Turns out it was just a coincidence after all.
Thanks to everyone for all the replies. Your help is much appreciated.