BK or Radio problem?

[hoober]

I have e-maxx with small BL motor and BK 7020 control with 4S batts (kinda mild set-up)

Here's what it does wrong. I'm not sure if it's a radio problem or controller.

Only when over 100ft away AND letting off throttle it is jittery or no-throttle until it gets closer OR I go back to neutral.

When running at close range it does everything right (even at WOT)
Wehn running WOT it does everything right (even at far range)

If it is over 100 ft away and you never let off the gas it's fine. If you do let off the gas it will be very jittery if the vehicle is allowed to stop, if the vehicle isn't allowed to stop there's steering perfect, but no throttle until stopped.

Is radio problem or control hitting some safety or cut-off?