Why doesn't my player go into standby mode when I turn off the ignition?

Your mentioning "Volkswagen" brings this to mind, particularly the part about "If the player keeps on playing when you shut off the ignition, you may have the 12v permanent power swapped with the 12v ignition-switched power. Volkswagen and Audi cars are notorious for this problem, since they swap those lines on the DIN connector. Simply swap the pins on the wiring harness to fix it.

I know that your problem isn't about going into standby mode, but the swapped connector wires may be at the root of your problem if the installer had to make some accommodation to allow for it.

tanstaafl.