To troubleshoot your issue, do you have access to NCS and an OBD cable?
I havent read through the thread, so please help me out here..
Do you have the iDrive? If yes, can you send me the CIC.trc file? else, it will be the RAD2.
In general, if you have a combox, the mic is wired to the combox , and the radio expects the mic signals to come via MOST..
It could be that while coding, the mic might be set to as being directly connected to the radio, which is not the case..