Hi. Got a sram x7 rear derailleur . Put on new caset and chain now rear mech won’t happy sit in high gear without jump up one.
H SCREW COMPLETELY DIS ENGAGED
CABEL UNDONE
Any ideas? Thanks in advance D

Correct lockring used? If it’s too big then the chain will jump.

Mech seizing would be the other obvious one

Or possibly a bent mech hanger.

Mech sizing?

Put a washer between the mech and the frame. My Mk 1 Soul needs this to work properly.

Does the new cassette need a spacer between it and the freehub? Some do and some don’t even on the same wheel, although you might struggle to get the lockring on with a spacer that isn’t meant to be there

My Hardtail frame also needs a spacer / washer between the frames mech hanger and 10 speed XT mech itself.

It just spaces it out a little so it drops into the 11t cog properly.

i think its due to the mech hanger being a bit thinner than normal in my case.