I couldn't see if that was a digital servo or not. How much spring do you have on the brake return.

It's been a while since I ran a non digital servo or nitro, so I don't remember. Try this out. With everything turned on and the Tx in neutral position, see if you can move the servo horn. If you can, it might be pulling the throttle open when you move the throttle to neutral position after braking, due to excessive return spring on the brake.

I like digital servos because they are always seeking center when the throttle is in the neutral position, but this is also why digital servos also eat more juice.