Rear Derailluer Issues
About 90% of the time when I stop pedaling, my rear derailleur likes to lift up, creating slack in the chain, for about half a second and then it'll go back to normal. I took it to a repair shop where I received a tune-up and had the chain and gears cleaned and oiled, yet it still does it and the guy can't figure out why. Please help. I have videos of the problem that I can send if anyone thinks they might know what the issue is and needs more information. Thank you.