Bit of a head scratcher, any thoughts please?

XT 1×10 with a TRex and a wonky ring on the front, on an Evil Following. It’s worked perfectly in the past.

Now, upshifting (easier to harder) from the biggest sprockets is working only on the workstand, when it works perfectly. But stood on the ground, even unweighted, the cable released by the shifter is not being taken up by the mech. Same happens when ridden, or bike upside down. I can physically pull the slack through by hand at the RM.

As far as I can see the hanger is dead straight, the RM is not damaged.

I also tried it on the stand with no pressure on the shock, in case the frame shape loaded was an issue. It still worked on the stand with the shock depressurised.

I changed the cable but the cable that came out looked fine – no kinks in it that would provide resistance in the sheath.

Any thoughts please? Ta.

Take it all apart and start from scratch?
Is the mech catching on something?
Sticky pivot?
B Tension?

I have had this when wrapping a cable around a cammed mech the wrong way.

Check the fitting instructions for the EXACT model of mech you have.

thx chaps.

More B screw sorted it.

That’s annoying, in a good way. So much for being a competent home mechanic.

Thx for chipping in both.