Take a couple pieces of Supervisor Tape and put in the channel for the barrel and tighten it up. It will stay. It will be hard to pull off but it will stay. The forend moving under recoil is what it is. Also make sure the screws are not bottoming out giving the effect the forend is tight.
Simple no fuss no muss and other uses for the supervisors tape.
In other words 2 faced tape slang supervisors tape if you get my meaning.