I have been riding my Mt.bike and i had no problems with it whatsoever and all of a sudden my gears skip when i ride. I went to a bike shop and they said that its because my suspension was moving my bike around in the middle and it was changing the angle of the front and rear cassette and that's what was causing the skipping. I tightened the suspension and it keeps skipping.
Then i went there again and they said my chain was old. I got a new chain and it still keeps skipping. I was thinking of changing the cassette or the derailleur. What should i change?