So
The newest quirk to pop up for the first time ever. Select an audio source and it plays for a minute then goes away even though the audio screen is still active. Manually turn it off and the screen says Radio Off but the last selected audio source starts playing again. Manually turn the system on and the sound goes off.

 

What condition is the battery in? If it's getting old & discharged, it's often the cause for these unexplainable gremlins.

To reset everything, disconnect the battery for >10mins.
Be sure that you have the radio code! If not you can try this trick;
Press these 3 buttons; A.Mem , >> and PTY at the same time and hold for a few seconds.

If the battery off doesn't solve it, then i'm out of ideas...

 

New battery, so that's not the issue. If I press the 3 buttons, will I need the code?

 

The trick with the three buttons works if you have the original head unit & the car, but you've lost the code. Press the buttons when it asks for the code. If you have the code fine, but the three buttons should also work.