I'm going to guess that the cause is the action wasn't making firm contact with the pillar when it was bedded. Then when you tightened it up, the action wedged the laminate apart. I bought a BVSS recently, which was trying to do the same thing because the action was bottoming in the stock before it contacted the pillar. (because when Savage sanded the action, they took off too much material around the rear action screw) I knocked out the pillar, took some of the shoulder depth off in a lathe, re-bedded the pillar, end of problem.