I am a RH split finger shooter, and I just went through this with an instructor (first time I ever used one in 40 years). What I learned from him is this. If the shot hits left and your arrows group, it is too much pressure on the bottom finger, or you are overdrawing past your anchor point. If they hit right, it's too much pressure on the top finger. I have discovered this to be true for me, and I correct accordingly. As a test - nock the arrow, close your eyes, and slowly draw the bow. Keep your eyes closed and you will be able to feel the finger pressures. The middle finger should have the pressure. If you do this with your eyes open, you can't differentiate the pressures.
Good shooting, and I hope this corrects the problem. I know it can be frustrating.