It sounds like it is drawing too much power. The 7700 loves voltage and does give packs a workout. Might be drawing too much power away from the receiver.
You might be right because the way it sputters,it acts like the radio has a glitch.
What if I Run a seperate receiver battery pack like the Nitro powered cars need?
I needed to do that with brushed motors using just a micro switch and have done it also with ESC for brushed motors a long time ago.I think I had to have only the white wire hooked up from the speed control and had the reciver pack hooked into the receiver.
Can you do the same with Brushless?