Unfortunately, of the 3 NEQ6's I owned, I found this asymmetry in 2 of the 3. the third one had been "hypertuned" and had relieved this discrepancy (and it did track and guide flawlessly - thanks Grady!
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Of the 3 HEQ5's I have owned, ALL did it.
My advice is strip them down, rebuild them, using good bearings and delrin washers. They NEED it.