Been riding with E6100 system since January, with about 450 miles use. Periodically I get clunking noise when cranking. I've found that when bike is in this state, reverse rotation of the crank causes reverse rotation of the chain wheel, whereas chain wheel normally only rotates with forward cranking. It is as though something goes wrong with whatever ratchet devices normally ensures only forward rotation of the chain wheel. I've found that a quick reverse jerk of the crank stop the problem, but sometimes a few shots at this are required. Anyone else experience similar, or any expert theories as to what might be causing this and if there is any adjustment or lubrication that would remedy..?