Hi Andy,
The only know problems at Southport where in the old days and some old metal caravans in the park nextdoor and 27/40mhz radios.
There is nothing underneath apart from old rusty pegs and plastic mesh when we had grass.
A guess( by reading your other thread on this) could be you speedo not providing enough power to the Rx and if you have not got a built in failsafe it could be on throttle/last known input, and not brakes or neutral.
I had a home made alu chassis a few year back and that caused me a problem on that day until i bent it
