You were dead on with it being caused by the APIM. The service manager I picked it up from claims they did a hard reset on it that can only be done once and it is now working. He let me know that if it happens again that they will have to replace the module and he has been cleared to do so at no...
As of 3 days ago I've got 0 audio. When I try to turn the radio on it continuously turns it on and off but no sound plays. No voice prompt when using the NAV system, no sound when I try to have it read texts, etc. I've tried some random fixes I found online like locking and unlocking the doors...