Is the wiring in the car old?
Sometimes older wiring can have lots of small breaks in some of the wire strands which will spark etc, but can't be seen.
Tried a voltage protector (capacitor) in the receiver?
Aerial wire trimmed to a dodgy length?
Just a few possibilities.
What's the difference between this setting 3 and the other settings?
Xray T4'16, T4'14 (Wet Car)
Xray X12 2016
wlrc.co.uk (West London Racing Centre)