Audi A6 C7.5 Reliability

[PistonTim]

We took delivery of our 2.0 TDI ultra s-tronic in late March and the car has spent more time back at the dealer than with us. Most of the problems are around the stop/start system which although has been less invasive with recent updates had twice now caused the car to stop dead across the middle of roundabouts with a 'stop/ start system deactivated please restart engine manually' warning, this also happens at other times but in less dangerous situations!

Audi have replaced the mechatronic unit (4 weeks!) but the problem has come up again, this time they are saying the camshaft adjustment solenoid is at fault and needs replacing.

Could this cause the stop / start failure or are they just grasping at straws?

Car is a company car (perk) and I am seriously tempted to reject it at this stage!