Engine Seizes with starter installed

I have a 98 Contour in the shop with a 2.0L 4cyl. It ground over very hard and locked up the engine with the original starter (assumed defective).

#1 Replaced starter with new starter.

#2 Same problem. Car rolls over hard, don't start & locks up engine....can't be turned over with breaker-bar on crank.

#3. Removed starter, car turns over freely with breaker bar.

#4. Installed 2nd new starter, same problem.

#5. Removed spark plugs with starter in place, still locked up.

#6. Loosened torque converter bolts, verified flex-plate wasn't loose.

#7. turned engine over without starter in place & inspected gap between flex plate & a stationary position on the bell housing. Uniform gaps while turning over.

#8. Verified that vecicle came with and called for a 10 tooth starter.

Still same problem.

Any ideas??

are the accessories spinning freely? locked waterpump/ac pump could cause this too.

accessory belt is off.

So whats the flywheel look like?