i've tried it with the only other bluetooth device that I have, a nexus 10, which is also running android 4.2.2 and initially it had the same problem (albeit with the nexus 10 i had the micro HDMI hooked up just as shown in the installation manual rather than with the slimport adapter required by the nexus 4)
I've tried the whole reset/unpair, turn off the phone, reset the head unit etc. The issue has actually gotten worse.
I could previously connect my Nexus 4 as a "bluetooth audio" connection and stream anything from my handset that way, but that won't even connect anymore normally-