I have a YHM "build". Purchased a complete built lower and a factory complete upper with the 14.5" barrel, pinned Phantom MB and free-float barrel. Integral flip-up YHM front sight. I bought a $55 YHM steel rear BUIS off GB, have to dial it quite a few clicks off center to the left before my shots print in the bullseye. No issue when I had a GGG BUIS on there. Ideas?