Speed passion reventon R cutting out to half power?

[vrooom]

I have speed passion reventon R with speed passion 6.5R It reduced the power to half after 3-4 mins of racing until I switch off / on the esc.. the speed/power is restored.

the esc run on blinky mode Stock0 profile. has thermal off, lipo cut off voltage is 3.2. temp on esc after race is 60 degrees. motor isn't warm. lipo volt after 5 min is around 7.85v no loose connection or anything.

So what wrong with this esc ?