My targets get wonky if I brace the rifle under sling studs, either front or back. When I have been in a hurry to shoot and not paying attention to how the bags have "migrated", it has caused lots of befuddlement for me in the past, and now, particularly when I shoot off someone else's setup, it is one of the things I double-check. I'd start there.
Binding of the action with the action screws tightened sounds wonky. What do you mean by "tightened"? Were they torqued to spec, and then binding, or did you tighten them too tight and then have to back them off?
