[tobnpr]

If it were "my gun"...

Assuming you have confidence in your smith, and that the borescope of the barrel showed no issues...I doubt it's a hardware problem.

You mentioned the receiver is bedded.

Does it have pillars installed? Without pillars, action screw torque is even more of a variable. While the action won't compress against the epoxy, the bottom metal sure will against the wood stock as the screws are torqued.

I would re-do the receiver bedding, and install pillars. Not a tough thing to do, a few hours work or so- and absent an issue with the barreled action, that's the only variable left. Grind out 1/4" or so, and have another go at it.

I'm a proponent of not using screws to hold the action in place. Electrical tape, wrapped tightly and evenly the length of the action avoids placing stress points on the action.