While on the subject of strange happenings with the head unit ?

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Has anybody picked up on the fact that the front screen will pick up finger touch, with a “Beep” even when the car has been shut down for hours !.
I found this out a few weeks ago, when cleaning the inside of the car.
The car had been sitting powered down all night, I wanted to clean the front touch screen.
I sprayed a small amount of glass cleaner onto a fine micro fibre cloth.
While I was cleaning the screen, one of my fingers contacted the screen by mistake.
I heard the info unit make that “Beep” that you hear, when you touch for a command to be actioned.
I thought ? I was hearing things at first !.
But no, every time I touched the front screen with my finger, it would “Bleep” back !.
Info switched off and car powered completely down for over 8 hours.
There must be a very small amount of current being drawn, even when the car is powered down.
Try it for yourself, I have not lost the plot completely ( not yet anyway ) ?.
Not enough down to flatten the 12 volt battery ?- but the there does appear to be some sort of phantom drain ?.