Funny is that when i installed all user regions (without bootloader), radio normaly normaly boot that version. Maybe I'm wrong but it looks like one of setting or something is just stored in different area which brick device when it's from original rom.That is because your head unit is not compatible. Also the process you described to get the communication going is the key indicator that something is off.
I suggest you restore your backup.
We can try to troubleshoot it after if you can share high resolution pics of the motherboard back and front