Thanks for the input.
@otsdr It isn’t a Shimano direct mount hanger. I’d bend the hanger if I could, but it’s about 5mm thick dog-leg shape and when I tried that it was really difficult to budge it, then it snappthat’s)
I reversed the axle in the hanger, mounting it outboard, to demonstrate that the dropout isn’t perpendicular to the axle. However the socket.
@Paulwf My mech socket isn’t aligned with the axle, so the jockey wheels don’t align with the cassette or the wheel. I started out with a Park Dag-2 alignment tool but the thread on that is a different diameter to the socket in the hanger, and it requires more clearance than I have. It did confirm the misalignment of the hanger and helped me break it.
My other GX bike has clearly aligned jockey wheels and cassette.
From previous experience of bent hangers, I’d expect skipping gears from this.
@Mikertroid Interesting. Shop should have picked this up on setup. If the hanger is bendable that’s a quick fix; although if the underlying issue is the dropout it’s a warranty issue. Takes a bit more work to prove that though.
I’ve reached out to the manufacturer to see what they think.
Another way of fixing it would be to shim the mech hanger, about 0.8mm higher on one side than the other. Not sure how to make such a shim though. 3D printing? :)