JD 345 PTO Switch Overheats and Fails

Sooo... A couple months ago my brother gave me a 1999 345 with the liquid cooled engine, hydraulic deck lift and power steering. It's seems to be in pretty good shape. It didn't take much to get it running. I've put a few hours on it since.

Today the blades stopped spinning while I was mowing. I checked the electric clutch by applying power directly from the battery. It worked perfectly. I checked continuity between several pin slots on the PTO plug and the pigtail where the electric clutch plugs into the harness. I had continuity for both the wires going down to the clutch. I also had power coming in to one of the slots in the PTO switch plug.

So I checked continuity between pins in the PTO switch, and based on a YouTube video I saw, the switch clearly wasn't operating properly. There was no continuity between pins that there should be continuity. I checked with the switch open and closed.

My neighbor has a few 345s of similar vintage. At his suggestion, I scarfed a PTO switch off of one of his machines and put it on mine. It worked perfectly. I started mowing with it, and after about 5 minutes the blades stopped spinning again. I parked the mower and pulled the PTO switch. It was hot to the touch. And, much as I suspected, we put it back on his machine and it no longer worked.

So, does anybody have any ideas what could cause a PTO switch to overheat and fail repeatedly?

Also, a couple hints: I replaced the ignition module with an inexpensive unit. The old one had the eyelets broken off. I liked the inexpensive Chinese ones better than the John Deere unit because they were potted. And, it was a 1/10th the cost of the ignition module from John Deere. Also, when I got the mower, the PTO switch had been replaced. The one attached to the dashboard was not hooked up. But there was a "new" switch plugged into the wiring harness and just hanging there. So clearly the PTO switch had failed in the past.

Any ideas would be greatly appreciated. Thank you