Hi
I had a similar problems in the past with my cassette.
There are commercial tools available to check for sprocket wear,but I check mine with the blunt end of a 10mm twist drill bit .
If the sprocket is in good order the 10mm drill bit will fit snugly in the valley between the teeth and will not rattle side to side.
Try it on a gear you don't often use for reference.
If there is anything more than a slight bit of play your cassette is on the way out .
I change my chains at 0.5% wear and find the cassettes last a much longer.
If you dont fancy the 10mm drill route,putting a new chain on will confirm a worn cassette , the new chain will jump more than the old one did on a worn cassette.
If your chain and sprockets do turn out to be OK , the ratchet in your free-hub may be slipping occasionally this can feel like your chain is jumping.
Anyway good luck
Paul
I had a similar problems in the past with my cassette.
There are commercial tools available to check for sprocket wear,but I check mine with the blunt end of a 10mm twist drill bit .
If the sprocket is in good order the 10mm drill bit will fit snugly in the valley between the teeth and will not rattle side to side.
Try it on a gear you don't often use for reference.
If there is anything more than a slight bit of play your cassette is on the way out .
I change my chains at 0.5% wear and find the cassettes last a much longer.
If you dont fancy the 10mm drill route,putting a new chain on will confirm a worn cassette , the new chain will jump more than the old one did on a worn cassette.
If your chain and sprockets do turn out to be OK , the ratchet in your free-hub may be slipping occasionally this can feel like your chain is jumping.
Anyway good luck
Paul