The front ferrule is the flimsiest part of the M14 accuracy formula. The entire front end is held to the barrel with a bent lip on a sheet steel stamping pressing on a press-fit stamping (on the synthetic stock at least). It almost seems like a Friday-afternoon rushed decision that was never reexamined. If I had a million dollars (to buy CAD-equiped machine shop, not to buy Kraft Dinner and Dijon ketchup), I'd try to machine new ferrules. Ones with firmer keepers for the top handguard, thicker cross section and maybe even an adjustable set screw for tensioning.
On the other hand, maybe your stock is just flexing too much, or warped and not resettling properly.