Sorry for bringing this thread back from the dead. Thought I'd reply instead of creating a new one.
My NBT unit is also having this problem, frequency is about once a week, but I only drive this car on the weekends.
Screen randomly goes to NO SIGNAL as in pic, I suspect the NBT-to-Screen harness or NBT-side connector to the screen is bad. System stays like this for about 1-2 minutes before NBT self-reboots and system recovers.