Adaptive cruise control not working.

2013 V8 deisel Toureg RLine with only 145,000 kms in excellent condition.
Love this car however. ACC (radar cruise control) not working. Previous original owner had it to multiple dealers under warranty and after warranty and no one was ever able to fix it. I am not willing to waste hard earned dollars and time making the same expensive mistake. Last time I posted this I was advised to have the battery tested. Did that and it was perfect. Have not taken it to a dealer for a scan as I dont like being ripped off and they cant fix it anyway. Anyone out there with a similar issue who knows how to fix it ?

Please dont suggest getting a scan as thats been done by experienced service departments at various VW dealers in Melbourne and was 100% unsuccessful

Also the only other issue is the drivers door red warning light which appears on the dash for no apparent reason occasionally, and you cant lock the car with the door sensor or the fob. It usually settles down by next morning and is fine for a few days until it happens again. I though it was being caused by the high pressure car wash, but it happened on a dry day recently and no water had been near the car for 4 days.
Any clues guys ?

Neither of these issues are battery related. It even happens after long trips.