I can only illustrate my own experience over 30 plus years. I read all the comments.
It is not your scope or mounts, I prefer a scope to be as low to the bore as possible, having said that this only effects the trajectory curve, not accuracy. It is not your scope. Some indicate that adjustable rings will vibrate loose, I have Sportsmatch Adjustable Rings on all my springers and I have never had one vibrate loose, however I do check all the fasteners once in awhile. I have never had an Airmax fail on any Springer including that hammer of a gun the Gamo Magnum. I suppose some do as any product can and will fail sometimes.
I had a .25 97 for a time, I was never happy with it and sold it. We all learn things the hard way most of the time, those heavy pellets that travel in the 500 fps range are simply too heavy for that gun and its designed spring power, to begin with you drop your FPE down to 10 to 11.5 pounds and the shot cycle slows so much you must have a perfect trigger pull and follow through each shot, it is not a forgiving gun. The best pellet in my copy was the Predator GTO. I could shoot an one inch group at 50 yards with it, provided I took my time and fully concentrated on each shot. The ballistic curve on that heavy .25 pellet at 50 yards with the rifle sighted at 35 yards was so extreme I was way down past the last mark using an Airmax 6 by 24 by 50 scope. I was in the guess it is here halfway down this little box situation. An extreme ballistic curve due to simply slow velocity. At 25 yards the distance you are shooting the GTO would shoot a ragged one hole. If.......if you had the perfect trigger pull and did everything correct. Even at that distance this is not a forgiving rifle.
My .22 HW97 shoots two pellets with fantastic accuracy. I have the scope marked for a quick return to zero when I change pellets. It shoots the 11.75 Predator GTO at 843 FPS and has a relative flat curve and will shoot paintballs at 60 yards and will consistently shoot one half to 5/8 group. It likes also the FX 18 grain and has the same accuracy, however it slows to 640 FPS and the ballistic curve is extreme at 60 yards and I am in the middle of the first lower square box with an Airmax Reticle. Also I average 16 to 18 FPE with the .22 which exceeds the .25 due to the velocity difference.
My .25 was never forgiving. It took extreme concentration to shoot it, where as the .22 is very forgiving as as long as you get a decent trigger pull it forgives all t he other things we as shooters tend to do.
Just saying as was my experience .
Cheers
Kit