Ultegra shifting woes

I’m having problems with my R7000 groupset. When i’m sat in the middle of the cassette for a period of time, when I go to shift up the cassette, it jumps up 2 then skips back one. If I tried it immediately afterwards, it doesn’t happen. This happens when i’m trying to shift up one, so just a short push on the lever.

When I put it up on the maintenance stand, run through the gears and adjust the tension, it doesnt happen and goes smoothly up and down the cassette. As soon as it goes on the Turbo or out on the road, it does it again! Thoughts?

The essential difference between being in the stand and used in anger is the amount of power going through the drivetrain, so I reckon worn chain and/or cassette rather than an actuation issue.

Could be one of many things, sticky cable, worn jockey wheels or an alignment issue. Strip down and clean probably required, or leave it and just learn to live with with it.

Get a rear mech alignment tool and check the mech is straight before trying to fix anything else. Saved me countless hours and frustration fettling this shifting issues in the middle of the cassette.

Cheers guys, got the bits I’ll check the mech and chain.