Bad treads on upper mount, replaced with a thinner bolt.
Breaking the nose on the starter. Those the upper stud center the starter or is there something else wrong? Bent ringgear on the trans?

The upper bolt hole in factory starter is way larger than the bolt, the lower stud hole is closer to the stud's shank size. The starter is centered by the nose and kept from rotating by the bolt/stud.

fyi my power master starter comes with a bushing for the upper bolt. In the past they did not and it broke its nose. they paid for it, shipping included just saying. you may be dealing with stock one ,just passing some info. pat

Here's a fix: Buy a tool bushing; MSCDirect,McMaster-Carr, Grainger ...?? (for 7/16 diameter fastener)the thickness of the starter flange. Machine or carefully file the flange upper bolt hole to accept the bushing being pressed in. Not sliding fit,.0015" interference fit. No more starter issues. You have to do this for using a mopar starter with an Ultrabell adapter for PGlide. You have to have the top fastener aligned in the receiver/bellhousing flange with the starter itself for optimum or even consistent operation or meshing with ring gear on the flexplate. You can cut the nose off the starter as well if the nose doesn't center or is too long to the hole in bellhousing. This was an uncomfortable learning experience, but works great now.

Ooppsss,.. all the above is predicated on having a 7/16-14 NC thread for the top fastener required for the starter. Fingers go too fast sometimes.