If a tang screw adjustment corrects this you either have a stock slightly over or under inletted. Under is easier to fix, just inlet it more. Over inlet can be a real problem if the wood is not slightly proud of the metal. Never figured out how to stretch wood more.
I had a Sterlingworth pin gun with a miller trigger which had been restocked. It had both wood interference problems and was over inlet. Easy way to fix it was to just restock it. Well not the easy way but the one I took. You could try the tang screw approach first. Or even measure the old stock and new stock. Most likely you have a very slight wood to metal interference problem. Plain terms, it hits somewhere it should not. Have you smoked it and looked for any spots?
