MMI shuts off after starting up

Hi guys 

My a4 2015 multimedia mmi started misbehaving, the dab stations on the radio started disappearing no reception so switched to fm then over a few days these dropped off no reception 

i thought bad earth antenna so then tried to play media via phone, I noticed the mmi was taking a while to come on, it now only displays splash screen then shuts off.

it sometimes starts nav initialising but shuts off pretty quick and black screens.

i took out radio unit from boot took it apart to check for bulging caps and dry joints but all looked good.

now I’m stuck still feels like a bad wire but not sure what to do next

If it was a fuse it would not work at all 

Thanks