Owner's Command can't detect radio/DVD after exiting Engineer's Command menu incorrectly (2009 W212 E550 RHD)

Unfortunately, whilst I was in the Engineer's Command menus I got distracted by a phone call and Command powered itself down without my selecting 'End".

I was in the HW Menu #7,sub-menu 7.3 " Market/DVD" audio menu to see if changing the market selections within 7.3 would stop the chime (it didn't). When Command crashed out due to the power down I found all of the 7.3 sub-menus greyed out except for 7.3.4 which selects for either single or stacker DVD player settings; now this is the only changeable option I have left from 7.3's menu.

The bigger problem, however, is the entire Audio system is not being detected at all (I got a message in Ownwer's Command to this effect), and I can't change any of the greyed-out settings in Engineer's Command 7.3 to reset the market/region, etc, to fix it. I tried removing radio fuse #26 when that didn't work, I disconnected the battery to dump any memory-resident glitches, but that made no difference either. Everything else with the car seems fine (a scan using my iCarsoft MBII indicated no faults) but all I get is static through my speakers, although the volume and controls mute still work so the amplifier is functioning. It seems to be just the radio and DVD that are affected, but I'm currently at a loss regarding a remedy.

Thanks in advance for any help with this.