This should help explain the K-bus:

https://www.bmwgm5.com/K-Bus_Troubleshooting.htm

I read your thread. Sounds like your K-bus is also crashing (I think it can get corrupt data from a component which causes the crash) which is causing your various light issues etc. Once you reset the K-bus (by disconnecting the battery for example), things should start working again, for a while. At least, that's what happens with my X5. I now suspect either the Nav unit in the boot has an intermittent fault, or wiring is damaged on the audio system somewhere. I swapped my front screen for one with no blemishes, so that's an improvement, but it still flickers on and off so whatever is causing that could be what's crashing the K-bus.

You could have a permanent fault though I guess, so even a reset doesn't get things working?