I have a fixie with flip-flop hub, I usually ride with the singlespeed side, but once I want to use in fixed gear, but when I apply back pressure on the pedal, or pulling up with the strap, like trying to skid, the cog slip or skipping some teeth, I can't describe well how it feels. The cog and the lockring was tightened up, but the problem isn't gone.
Any ideas?