Originally Posted by
Tomo_Ishi
You could have loose axle lock nuts. You know the corn-nut and stuff. I had them loose on my formula hub before. It was slipping, but the cog-lockring were in tight. ... Check the hub axle, too. Takes a half a min to do it.
The slipping back makes me find this unlikely, I can't imagine pedaling forces getting your wheel to slip back into place, only forward, maybe I'm wrong, physics are interesting.