Every scope I've mounted on a springer does this to some extent. Some more than others. A shift of 2-4 clicks
@25 I'm chalking up to thermal drift. We have wide temperature swings and this seems to affect POI the most. My rifles will all hold zero until the Temps start changing.
Changing scopes has never solved the problem. My hunch is that the aluminum, steel and synthetic parts in a scope/mount/ rifle system expand and contract at different rates in temp changes.
Sooner or later they have all developed POI shifts that are extreme. Sudden 12-18 click jumps. Mostly elevation with small windage corrections.
In those cases changing scopes solves the problem.
It's frustrating to say the least. It happens on all my springers. I keep a paper target set up on the plinking range. I shift to paper to check zero when I miss a couple. If I shoot 150 shots in stable Temps I rarely ever have to re zero. In swinging Temps it's much more often.
Iron sights have never shown a propensity to drift. Day after day a zero check shows they are hitting in the same spot. But put a scope on them and things sometimes get funky.
I think a one piece mount does it worse than a two piece mount. I've tried loosening the front strap a bit and holding the scope tight on the rear strap. That seemed to lessen the creep.
I've noticed that if you optically center a scope on the bench and then check it after it's mounted things change a bit. The tension of the mounts bow the scope tube a little. I suspect this will change as things expand and contract. It may be why the POI shifts.
I've never lapped scope rings on an air rifle. But after a few years of constant scope issues I think it may be something that might help.