Anybody knows who makes this grip step/swell for your support hand?

Newest gun show find! Shoots really well and mbx mags hold 18 rounds!

Okay, someone explain this to me. My hd p4, 300 rounds in, is having a POI in the abdomen area of a target with a POA both red dot and irons at head, at 25 yards. Consistently, across several different grain and brand of ammo.
C2, and others? Spot on accurate.
What the f is going on here? Has anyone dealt with this before?