Something similiar happened to my Dad's E-Maxx running the Novak HV-Maxx. Steering would work for a bit, then go crazy, the motor would cogg and it wouldn't stop unless it had a rolling start. My Dad figured it was the motr, I figured it was the receiver/radio. Turned out to be the Reciever/radio, he was running an XS3 FM Synthesized and he swapped it out for an older AM combo, it worked just fine. I'd suggest trying another radio setup, it might fix your problem. Also, your gearing seems to be too high, you should maybe go with a 54 tooth spur, unless you have the 2-speed still running. Good luck fixing your problem.;)