a couple of lads at our bash using the same radio had the same prob,there cars had a mind of there own.
i had a dx4s which was doing the same when racing indoors at batley buggy club it would just glitch out and have a mind of its own.
horizon said it was a rf board fault.so they sent me another.
2 weeks later same again,returned radio back to them same prob.i did'nt even try the 3rd new radio they had sent.
i bought a futaba 4pls, that solved the problem.hope u get it sorted mate.