[tirving]

The inconsistency is like you and your form, grip, how hard you are pulling into the backway, and/or anchor changing a bit. IF you can consistently see bare shaft and fletched tear opposite left and right, that's likely contact. This will affect up and down too. But..... 20-30 yard bare shaft tuning will tell you a lot too; unfortunately, it might be a little harder to diagnose slight contact from bare shaft tuning. If BS hits left of fletched, you would be moving the rest to steer the fletched toward the bare shaft. But... if you have slight contact and your bareshaft is tearing tail left, you will be chasing your... tail
I would try and get as close to a bullet hole with bare shaft, then go to 10 or 20 yards and shoot bare shaft vs fletched and see what happens.