ZS180

A5 2012 2.0TFSI Cab:
The LH side boot indicator stopped working in December and the dashboard bulb failure indicator come on the first time starting the car up and indicating left. All other indicators and lamps worked fine. Thinking that it was the LEDs that had stopped working in the unit I got another one and tried that out with the same issue. The new light unit I tried on the other side and it worked fine.
The car went in for an Audi service and they spent an hour looking at it but concluded it was a 'wiring fault'. I took the boot lining off and could not find any evidence of broken wiring. Without a wiring diagram I couldn't trace it to the ECUs in the rear RH side wing.
About a month ago the RH indicator stopped working so when I turn left or right now the bulb failure warning comes on after first starting up the car and again all other lamps work fine.
I have heard that it is not an MOT failure as the wing mounted indicator lamps are still working.
Note that the boot indicators don't come on with the hazards on, nor when locking/unlocking the car. My local Audi dealer have searched the Audi database and don't have a tech solution on it.
To say the least this is driving me up the wall !
I would have thought that one indicator going could be a loose connector or broken wire but both going seems incredible?
A couple of days before the first indicator went I had the windscreen replaced and probably unconnected but the second one happened out of the blue. I do have the roof up and down a lot and the cable loom from the boot lid is flexed quite a bit but still seems incredible that only the indicator wires are affected.
The only other thing it could be is that the ECU for the boot lamps is malfunctioning in some way and perhaps needs a reset. I haven't found much in the way of controls in the convenience ECU tables (which i think controls the indicators) . If I could buzz out between the lamp unit connector and the other end at the ECU I could eliminate the possibility of a wiring fault. Attached photo shows ECU in RH side rear wing.
Any help will be gratefully received.
RH rear wing ECUs