hmm, I am sure you have tried recalibrating it to the tx, but throwing that out there. What if you try trimming the neutral until it start to move, then backing if off just a click or two so it will sit still, and punch it? I have had 2 out of probably 15 of the ezruns that acted funny. When you slam the throttle wide open, they would just sit there like they didn't react to the throttle input at all. The leds wouldn't respond or anything. It was only a slam from a dead stop. If you eased into it a tad it would take off fine, no cogging. Have you messed with any of the timing, or punch control settings?