FX DRS Classic SHP air leak problem

The ongoing issue with air leaking from the plenum on my FX DRS has returned. This was an eBay purchase and I’m guessing the seller sold it as new when they had in fact fitted and found out it leaked air. The mating surface for the o ring that seals the plenum to action of rifle has been machined to close to a chamfer around a bung hole so o ring keeps weeping.