starter hanging up

[merlin3]

on my big block c10 2wd my new starter was engaging but it would hang up on the flywheel,i thought it was a bad reman starter but when i installed the new summit mini starter i pulled the gear out by hand,meshed the teeth together to check the tolerance on the pinion i noticed the gear on the starter won't spring back and when i pulled the old starter i noticed the starter gear was hung up on the flywheel,any ideas what is wrong? thanks.[ i did not shim the first starter]