4 broken starter cones,HELP!

Tractor is a '95 John Deere 5200 w/3900 hrs. Owner replaced original starter after cone broke off the end with aftermarket starter, soon after this, starter did the same thing. When this happens the broke off piece falls into cavity and tractor has to be split to remove. Starter has been replaced FOUR times, it is broken at this time. Owner said mechanic said flywheel looked good last time in. Thinking of buying tractor and repairing , any help diagnosing this would be great.

Generally it's a bad tooth in the ring gear, but could the wrong dimentions ( holes drilled a little off, or the wrong nose ) giving it too much gear lash and allowing the drive to climb on the ring gear.

starter problem.

Thanks, that's a starting point, going to negotiate this week, with a front-end loader and new back tires, whats a good ballpark figure, tractor is average condition, thanks.