I had a similar problem in that guns that I used to shoot POA/POI all started shooting to the left. It was not much, less than a two inches at 25 yards. I could not figure it out and I checked my grip, had others watch me shoot, etc. Then one day I went to the range and all of a sudden everything was once again POA/POI. I could not figure it out.
Got home and told my wife what had happened with that day's shooting. She looked at me, looked in my range bag, and said, "You wore your old glasses today." Sure enough, she hit on it. My prescription changed and my new glasses had more correction for an astigmatism. Swapped glasses a few times during my next range session to prove it. My older safety glasses keep me POA/POI, and my new ones resulted in everything impacting to the left. Still need to talk to the eye doctor about it.