[Zippideedooda]

Thanks for your responses. The Led is 22mm behind the trailing end of the guide, so I suspect this could be the issue.
 The powerbase is 70cm from the curve before it, and I have not had any issues with any of my 30 plus other digital cars so I am not thinking this the cause.
 I will remount the chip so that it's Led is closer to the guide, and see if that corrects the issue. 
 Again thanks for all your imput.