I have an additional question, which I am not sure is related to my problems or a "feature"

When I give the throttle full speed and pull the brake fast, the servo just goes to neutral.
But if I relase the throttle and keep it at neutral for 0,5 seconds or more and then pull the brake it actually brakes.
I find that a bit odd and it often leaves me with a car that doesn't break when I want it to.

This is not related to the range between transmitter and reciever. This occurs even within cemtimers between transmitter and reciever.