It's something, patience and good methods are needed.
Back to basics, you need to check/re-check everything. I use several levels simultaneously (check that they agree with each other first, some are a speck off)
mine and friend's TTs
I once found a platter that was not properly seated on the spindle. off/on, done
I once found a TT that was sitting in a plinth, unfastened, another: one screw of 3 tight, the other two snug but not tight. An arm not really tight on the arm board, mechanic's elderly father forgot to tighten the wheel nuts om my wife's MGB,
recently found two removable headshells not perfectly parallel with the tonearm, put little 10mm diameter bubble levels on the headshell, and acrylic block with lines behind the headshell, not the arm for VTA
adjustable feet to level the plinth, I shake rattle and roll them to see if they settle different than they just were, and re-check after a few days.