I was under the impression it was when you fire in semi, but the gears dont make a full turn either because you dont hold the trigger down for a full revolution or were firing too quickly for your battery to cope and the same thing happens (a full revolution of the gears is not made).
Simple fix: Just use full auto
Its not difficult to pull one round off in full auto.
Better fix: Bigger battery
The better the battery, the quicker those gears will turn and make a full rev, creating a smaller window of opportunity for you to let go, miss time etc a trigger pull. You dont even need to upgrade Voltage. I bought a 8.4v 3300Mah battery to replace my 8.4 stock, and the rate of fire increased considirably.
BE WARNED: Your gun may not be built to withstand the stress of super high ROF and there is probably a massive discussion somewhere on here about this, so its up to you to work out how much you want to increase rof etc. Just dont be stupid and whack a 10.8v Li-po In there or you might create similar conditions preceding the event we know as the big bang.