Tracking sightron vs swfa?

All the Swfa’s are good but the fixed power x10 is the

“Legend” in toughness and reliability. 
You didn’t say what projectile you where shooting. Another possibility for your problem is that the bc of the projectile is changing as it slows down. In this case your scope may not be your problem. 
Does your reticle enable you to check you clicks are or aren’t accurate? 
Try holding over using your reticle instead of dialing and see what result you get that way. 
Even with very high end (expensive) scopes many competitive shooters will use a grid type reticle and hold over and off rather than dial. It means you eliminate any mechanical inaccuracies. 

 
I use Strelok Pro on multiple air rifles and powder burners. It is very accurate “if” and only if you correctly input all of the variables and only if your velocities stay within a pretty tight range.

Air rifle projectiles tend to be more significantly impacted by outside influences than heavier ammo making it very tough to be extremely accurate with a ballistic calculator. I’ve owned several of both Sightron’s and Swfa’s scopes and all of them tracked very well.

Bottom line is there is no substitute for practice and fine tuning your clicks or holds based on your individual rifle and conditions.