The best way to fix this problem is to wax everything metal EXCEPT the ferrule and glass the area around the front receiver ring, and the tang area, and also put a pea-sized dollop of glass around the rear of the trigger guard. Make SURE the screws are all waxed, and I use some wax inside the ferrule too. Tighten down the front screw tight as you would any other time but just take the slack out of the rear screw so you just feel it start to tighten against the ferrule. Stand the rifle up and let the glass harden for about 6 hours.

In 6 hours take out the rear screw and leave it out for now. Take out the front screw and re-wax it, and put it back in. Let the rifle stand for about 16 more hours.

Next take it all apart and clean off the wax and any "flashing" you have from the glass-bedding job in places you don't want it.

When you put the rifle back together this time the steel will not be able to flex. The ferrule is used as a depth gauge, but at this point any shrinkage of the wood that you have is not filled with glass and you will have 100% support where you need it.