Most likely AMP issue? If you understand how the MOST system works, you will know anything connected to that system can cause similar issue.
Amp normally fail when water is leaking through the left hand tail light.
And with these cars, the most common fault is from the ULF - bluetooth module. If you are in Melbourne, I can check this out for you in our workshop. Or you can borrow a ULF from someone to test it out. It's pretty easy to swap.