I had the same issue with mine recently. If you slide under the car you should be able to see the connector between the car and the bumper (its normally clipped to the metal frame). Un-plug the connectors from each other and give them a good clean with some electrical contact cleaner, particularly the connector coming from the car.
This solved my issue for a year or so but it reappeared last week. Being at home I decided to replace the harness cable (YMD001580) on mine (52 tourer). If you find that you have the older wiring loom (YMD112321) I have one here that I ordered in error you would be welcome to.
Not a bad job to do and you can also take the opportunity to seal the fixings that allow water into boot.
Rob
https://drive.google.com/open?id=1N3...HwHFCGgMt_A4Uy - With side carpet removed.