I’ll try cleaning the fibre optics and see if that works.

Yes I think any part of the loop can be bypassed. It seems to be that only the amp, the controller and the screen are essential.

If all else fails do as I did and disconnect the battery for a couple of minutes

before you disconnect the battery, just try removing fuse 49 and 5 mins later putting it back, it does not solve your problem of the AHU (Audio Head Unit ) restting itself every so often, but it does help many others with AHU issues