My guess would be that an action screw is possibly bottoming out and preventing the rifle from getting held firmly in the stock.
I'm no 'smith though. Its just kind of a logic thing.
I'd check the screws and then re-bed.
I agree on the front action screw, looks like the rifle is moving around in the stock a lot.
Can you see rubbing from the front action screw bottoming out in the screw hole?
David