car not quite powered off: dash off but nav on

Well, I just got back home, parked in the driveway and pressed the button to power off. Then I noticed the nav was still all lit up. The dash was completely dark except for the security light that always blinks when the car is off. But the nav was still all lit up. So I pressed the power button a couple more times and then it shut off completely.

Is there a scenario in normal operation where the dash would be off but the nav would be on? Has this ever happened to you?

Yes, pressing the power button without the brake depressed.

When you turned it off (without pressing the brake), you must have actually pressed it twice, which turned on the nav only. If you pressed the button again (without pressing the brake), everything else will power up, except climate control, and the car won't be "ready".

A third press will turn the car off, EXCEPT if you had pressed the power button that third time with the brake depressed will put in the car in "ready".

That makes sense. Must have accidentally pressed it twice due to switch bounce.
I guess that's the downside of a push-to-start vehicle.
Good to know at least it's not going berzerk.

It's happened to me several times. I don't think it's Tony's scenario because the nav doesn't restart, it and the radio just keep right on running. I kinda wish I could reproduce it at will, since I sometimes like to listen to the radio for a minute after I park, and it's a nuisance to have to shut down the car, then turn on just the acc mode.

FYI, if you have 12 volts going into the accessory plug, the Clarion navigation system will power on.