You're welcome Kaz, just trying to share what I've discovered.

Due to the angle the radio is installed and the location of the capacitors, the ZD807 area is affected by damage quite often.
I was surprised by the fact that so many OP amps are supplied with the 10 V reference created there. Even the volume and tone PCB are provided with V+ from there.

Another radio has very strange sound issues probably related to the audio path, too but I haven't been able to identify the problem yet.

It's good to hear the information provided is helping.