Hi, have you checked that your hanger is not bent, if this is the case, and I have many many when the bike has fallen over or when leant on, the hanger has bent and in a lot of cases has only affected the critical gears that you have mentioned. In your top gear i.e. 21 check the alignment of the jockey or take bike to bike shop as their is a special tool for checking frame alingment, hope this helps regards |Derek
