Newish Chorus 11. Changes gear perfectly. But in certain gears it seems to jump under power. The problem is it doesn’t do it very frequently, say once evey 30 seconds. Chain stays in the same cog and there are no extraenous noises which would imply the adjustment is wrong. Derailleur looks like it lines up ok by eye. Anyone any ideas?

Have you changed anything else recently? chain, cassette, rings?
skipping is a classic sign of mixing new with old around the drivetrain.

No, and the drivetrain is less than 500 dry miles old. The only other thing I can think of is that I had to do an emergency stop due to some dozy peds and then started off again in a high gear with a bit of a graunch as I changed down. Maybe a bent hanger? But I would have thought that would manifest itself as a reluctance to change gear.

Tight or twisted chain link.?

twisted link … i had almost exactly the same reason and result
as you.

^ That is exactly what is was. The connecting link had a twisted side plate. Good call chaps! Thank you very much. Let me buy you a virtual beer.

Isn’t it nice that 1 time in 100 when the problem turns out to be the easiest and cheapest to fix of all the possibilities.. 😀