NEED HELP: Winchester M1200 problem.

Ive had on old gent present to me a very newish, but old M-1200 12 gauge. Gun is old with less than 15-20 rounds thu it in its life.
Was brought to me in the exact same shape as in the pic.
The Slide Arm Bridge Retaining Screw was broken, thus allowing the FP & spring to come out of the bolt..thus jamming the gun.
We ordered two new screws from Gun Parts Corp., a repro and a used OEM.
He had the broken..NOT backed out...screw tapped out. I repaired it with the repro screw & blue loctite. She cycled like greased lighting both with me & him.
All pleased. Today, he calls..shot a polecat in his yard, and the gun totally locked up on ONE shot.
Brings it over...exact..same..thing. Now, the screw is broken off deeper than before. Was NOT over-torqued nor did it back out..it broke.
Ive got the other screw..the used OEM Ill use next, as soon as he fetches the bolt and has the screw tapped out again.
So, thoughts? What am I missing? It went together perfectly before, and again I was 100% sure all was well. What I did, was. But why is this screw broken twice now on a gun less than a box of shells thru it?
Trying to post a pic..

https://i.postimg.cc/5NZrG6L8/BOLT.jpg