If the CFA is changing the crosshairs then an easy-ish way to check that is to clamp the gun in a workbench (suitably padded of course) just enough so you can refocus the scope and move the CFA in and out without moving the gun. Choose something detailed at a distance where there is an overlap i.e. can be focussed with and without the 50' (16yds or so) then keep changing back and forth (CFA) until you are convinced that the cross-hair is always in the same place. Don't change mag while doing this. Then if you really need a mag change repeat the above at a different fixed mag and finally try zooming in and out but that can be harder to do with some scopes without moving the setup. It is not always easy to get a rock solid bench at a club ground but if all you want to do is check the optics you can do this anywhere (well not in public places, etc!).
You could then perhaps repeat it on the range but my cheapo workmate tends to wobble and sink in to the dirt at our club :-)
The 20-50 can be misleading if the turrets are not centered and I calibrate range and dial for a fixed mag (usually max) and wouldn't really expect it to be the same at other lower mags - or do the calibration at 20x and have 2 sets of charts? Seems crazy using 50x at 10yds but with these 15mm KZs it is all about the scope setup and hardly ever about the wind, etc. 15mms are a bit pointless and a bad pulse beat can jump it out of kill, now if they were 15mm kneelers hahahaha.
All the best