MM ESC cogging badly

[LiqrSicc]

I bought it used and wasnt expecting this. Cogs on throttle on 55t spur 28t gearing on my mini revo. adjusted the startup power and still the same. the lipos are Hyperion G3VX 35c so there is more than enough continuous amps to provide it. swapped in my neu 1112 and same thing. its not mild cogging either. the truck looks like it cant make up its mind and shakes until it finally goes forward. any ideas before I send it to castle?