digital servos pull alot of power so you may be going into failsafe mode at the receiver. I know you said you dont want to run a capacitor, but that may be your best choice. You may also be able to power your servo straight from the speed control. To do this the speed control will need to have a power line coming from it. The current Tekin controls have this to power them if you want to. I run Mod Truck alot so I need to run the cap on it to help. I also run a personal transponder which robs power from the receiver. Dont have to run a cap on the 2 wheel drive buggy though. I guess it is lighter maybe.