I have fitted a battery cut off switch which completely disconnects the battery and which I use every time I park up for more than a couple of days. I wonder if this is upsetting the overseer, although it is odd that it takes 30 minutes or so to wake up? Everything else resumes where it left off.
I'd be inclined to this line of thought. If you are cutting power to all the systems of the car, there is a likelihood that the systems that expect to have a constant feed of power (for example the CAN bus), albeit limited, will be confused by the on/off of a kill switch. It would create similar, but worse, issues to those mentioned by people questioning a failing battery.
