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hamcereal: Is there play in the derailleur, hanger bolt or jockey wheels?
Mine has similar prob, very low mileage ebike with BBSHD mid drive that wants to shift/jump under load in middle gears.
Replaced chain,aligned dropout, and hanger. chainline is fine
Cassette looks fine, no wobbles in hub. indexed.
Has some hanger bolt play, so I was planning to replace the Acera RD.
Ebay sent a counterfeit, worse than current, so am still trying to source one, but would feel bad if it is cassette.
I really see no evidence of wear on it. ? Don't understand post saying wear may not be apparent.
Cables look good, but if indexing OK, shifts OK when not under ebike load from Overpowered mid drive
could a bad cable do that? Not sure how.
My hunch is it is RD hanger bolt/jockey wheel misalignment that is worse under load, that I can't reproduce while watching it.
Just replacing stuff may get it, but is $$ and inelegant thinking.