First off “tuned” magazines do lose their tune. Is it all mags or a specific mag? Is it your 170 mag? I find those more troublesome.
Discrepency in reloaded rounds in COAL seems to be related to consistent bullet size. Die setting (if tight) should not differ from round to round. Try another bullet profile from someone else.
I run my completed rounds thru a Lee FCD and case checker and don’t really focus on uniformity in COAL and my Czechmate runs like a top. I use factory short tubes with an extension and MBX for 170mm for 100% function.