Only does it on the top 2 cogs of the cassette, its fine on the lower 7. Riding along on anything bumpy and it just ghosts on its own from middle to granny.
I have not changed anything or dropped it recently, but its started happening over the last 3 rides or so.
Checked for bent teeth on the middle ring , checked angle of fr mech, played about with barrel adjuster on fr mech and am almost certain its not lifting the chain off and dumping it down to granny.
Full xt driveline and Mavic crosstrail wheels.
Worn or stretched chain perhaps?