interesting issue happening. Engines a kaw fh480v ds20. Just started happening and atm intermittent, either starter gear (maybe called pinion gear, not sure) but will spin up and engage flywheel and engine starts or starter gear will mesh up with flywheel and here's my issue, it will not turn and pretty much stick. Times it will release but had to spin flywheel to release. starter motor works either way. Someone mentioned it sounds like an issue with the gear assembly but just wondering...
Starter gear sticking in flywheel
Starter gear sticking in flywheel