Make sure the cable is clamped in the correct orientation on the derailleur. Clamping it wrong can change the pull ratio a tiny bit.
Great suggestion, would never have occurred to me, I'll go check now
Also check jockey wheels, are they overly loose or worn?
@tmevans started
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Make sure the cable is clamped in the correct orientation on the derailleur. Clamping it wrong can change the pull ratio a tiny bit.