Hi all,
So after some three years of trouble free motoring I now have an error that I am struggling to find its cause
The error code that the iiid is showing is

P0575-20 Speed control malfunction - speed signal failure

But the symptoms are bizarre to say the least first I noticed that my airbag light was on and after some further digging I noticed that my rear wiper had stopped and also my rear brake lights were flashing like a Christmas tree, there is a clicking from the centre console that I am guessing is the DSC as I believe this is its location the clicking matches up with the brake lights flashing.

I have checked the battery it only 18 months old and shows 12.5 volt all day long and with the engine running I get 13.9 to 14.1 volt so I don't believe it's power related.
Have also done a battery reset and cleared any dash errors
I have checked for water ingress on both sides in the back and generally around the car and all seems dry I was thinking it could be water as it started in the morning after heavy rain that night .
I have also checked the under seat wiring connectors and the all seem to be ok .

So what I have noticed is if I start the car and clear the codes, it fails to clear the code but and this is the strange bit, if I then switch off the car and start it straight back up the air bag light goes out the rear wiper works and the brake lights stop flashing and I can then clear the code.
All is then good until I switch the car off again, then it seems to be hit and miss but more often than not the error returns .

Any help with pinning down what this error code is would be most appreciated