Romy G build

Has anyone had problems with the dust cover coming off an AK when the bolt carrier group is cycled by hand all the way to the rear? Just helped my son put a new Tapco G2 trigger in a Romy G kit and the dust cover seems to move to the rear and out of the notches under the rear sight when the carrier group is pushed all the way to the rear. I'm thinking the hammer is putting too much upward pressure on the bolt when it cocks. Got a new hammer with the Tapco but have tried both the old and the new one and have the same problem with both. I have read about this problem some where(can't remember where now) but they suggested filing some off the hammer and since I have two hammers I'm thinking about trying this. No need to tell me if I take too much it won't cock,we built this from a kit,populated the barrel etc. so I know how it does and is supposed to work. Any advice?

Romy G build