Did you ever flood it? Sometimes it doesn't take much to hydraulic (or Hydro-lock, or liquid lock ) an engine enough to put a little bit (or a lot ) of bend in the rod. I didn't think of that...Maybe those guys are right, and all it takes is a few thousanths to induce a bind...Hmmm

Are you using a starter box? That would make it real easy to put possably too much stress on the rod...
The engine doesn't nessessarily have to be locked up either, to do damage.