The radio in my VW Golf MKVI goes crazy sometimes. It is a North America Delphi RCD-310. There are also European and Asian variants of this radio (perhaps other regions as well). You can tell if you have a North American unit if the four “Hard Keys” are labeled as FM-AM-MEDIA-MENU, your AM tuner “stops” every 10 Khz, and the FM tuner stops on the odd .1,.3,.5,.7,.9 Mhz frequencies.
I also have a MDI (media device interface) box connected to it as well. One of the symptoms is “silent” AM radio, meaning you can select a station, but no noise is emitted from the amplifier. Another symptom is MDI folder navigation and selection behaving strange. I’ll let you in on a secret. It’s like every other computer problem – just try rebooting it. But how can you do that without disconnecting your battery? Here’s how. Power on the unit. Once the unit is on, hold down the power/volume control for about 10 seconds. At the 10 second mark, the unit will immediately power off and reboot. It’s non-destructive and will preserve your radio station memory presets. That’s it! It should work correctly for quite a while before needing another reboot.