Mine does the same thing at full throttle. i tried redoing my batts and adding a ubec, droping the receiver pack, and will test tomorrow and let you know if it cured it. my ib's were done in a stick pack...
"if you've got something to say, say it peacefully"
What about gearing? Have you tried gearing a bit lower?
That would reduce the current draw - a 7 turn 1940 must pull a sick ammount of current at the best of times - if it's over geared, i shudder to think lol
Check things are nice and cool - packs, heatsinks etc