861 Starter won't disengage

Tractor was running just fine until it stalled and I tried to restart it. When I did the starter wouldn't disengage.
I removed the starter and noticed that the bendix gear was stuck. I took it apart and didn't notice and damage so i reinstalled it. Same thing happened; tractor started but starter stays engaged.
Some have suggested it's the key switch and/or the starter button that is still sending current to the starter. I ordered new parts today.
Any advice out there. It would be greatly appreciated.

Before installing any new parts, without knowing what to replace cam damage the new parts and be a waste of money!

Need to determine if it's electrical or mechanical.

Electrical:
First, disable the engine from starting. Be ready to pull a battery cable. Try the starter, see if it stops cranking when you let off the switch. Try it several times if it stops cranking. If it always stops, the electrical is not the problem. That rules out the ignition switch, solenoid, or starter contactor, which ever that tractor has. If it does continue to crank, disconnect the cable from the starter, track back from there with a test light, see why the power is still on the cable.

Mechanical:
The older tractors that rely on the "spin out" type starter drives are designed to engage the flywheel gear and lock in the engaged position until the engine starts. The drive is then spun up fast enough for the lock to release and let the drive retract out of the flywheel gear. Possibly the unlock feature is bad and mechanically holding the drive in. Try starting the engine again. If the starter stays engaged, try bringing the RPM up off idle. That may kick it out. Either way, the starter needs to come off and be inspected to see why it is staying in. Could be a bad drive, or just needs to be cleaned up.