Hey there , so was it the ESS or the driver ? Did you try running your setup without ESS?
Good day, It was the motor driver. I still used the ESS when testing the new motor driver. I'm not sure if it is still necessary to use it, however I have it so I might as well. I wish I had taken a video of the different ways the motors ran with out the ESS and with it, then with the old motor driver and the new motor driver. I know it would have helped me to see something like that on YouTube because I thought the motors were running smooth after installing the ESS but now after seeing how they run with the new motor drivers I know they were not running correctly before.
Hope this answers you question. Let me know if you need anything else.