MMM issues

[SV6000]

Hi guys i am having a problem with my MMM in my truggy and was wondering if anyone could help. When i pull the trigger to get the car moving, but only at a slow speeds, it moves off slowly as normal but after say five seconds accelerates off to 1/4 throttle. I have tried playing with the settings on the MMM and changing the firmware from 1.30 back to 1.24 and nothing seems to be working. has anyone come across this problem and know how to fix it. My setup is MMM, 1521 1Y on 6S Hyperion 45C