Sorry I just came back to the thread. You got a better deal than me! The SOS error is if you have the BMW assistant from the factory. It's the button up near the interior light/rearview. Looks like this:
The SOS error goes away and I've never even used it. Does not affect the head unit.
The other issue I had is somehow my temperature units went from F to C so now my outside temperature and HVAC controls are in C. I can not change them back because of the SOS error since it comes up on the little display in the gauge cluster and you need to use the stalk to switch units of measure and the SOS errors stays on the display for like 30 seconds.