Wild guess, try turning up the throttle endpoint on your radio some if you can. I've heard of situations where the full throttle drifts a little, then you do/don't get the boost/turbo/whatever to kick in. Could be the heat after running a while changes things???

Or a dodgy connection somewhere as already mentioned, that again heat is affecting? What if you switch batteries quickly after it starts rippin', that might eliminate the battery (which I don't think it is).