Sounds to me like a classic example of someone assembling the solenoid with grease or oil, which over time collects dust and dirt. Should use liquid graphite.
If the starter drive actually does not line up with the flywheel check the starter mounting bolts.
Hard to say without seeing it, could be solenoid, starter drive, If you want a really nice starter replace it with the QDJ1332A reduction type starter, it spins faster and is a much better quality starter than the QD100C3
I forwarded the Pics you sent me to the Shop, Jerry should be contacting you.Hopefully we have one that will work.If not you can try FarmBoys Tractors, they also sell Rhino parts