Feigao 7L, Warrior 9920 + 12 GP 3300 cells = hot?

I got a 9L today and it works fine so far. Had to put new plugs on the controller, which isn't fun if you have 2 cables from the controller to put into 1 4mm gold plug.

The strange thing was that everything went crazy when I tried to accellerate, steering started to act up and it accelerated and braked by itself. After quite some playing around I found out that it does this if the receiver is mounted on top of the Hitec servo (which worked for weeks) or if I touch a screw with the receiver.
For now I put a folded handkerchief between servo and receiver which seems to help. Only on fully throttle there's some wiggling of the front wheels (maybe normal?).