Occasionally, when I try to open the tailgate, it remains locked and wont open. At the same time, the window hatch also wont open.

I find that if I lock and unlock the car with the key a few times it will eventually open. Sometimes I have to lock and unlock the car and then use the button on the drivers door to unlock the tailgate and hatch but even this can be hit and miss.

It seems like there is no power getting to the tailgate area. When there is power to the tailgate and hatch, they work as expected.

I had the car scanned with PIWIS and it isn't showing any fault codes. A new battery was fitted 12 months ago and consistently shows 14 volts on the gauge.

Any clues on what could be causing this or if there is anything I can check? The car is a 2008 957 v6 and the tailgate is not a power tailgate.