Some car USB act as a memory stock reader, ie put some mp3 on a usb memory stick and car can play them. So when you plug in some dash/action cams the car tries to read the contents, so camera goes in to storage mode.
Quick fix is to use the cigarette lighter adapter to connect to 12v socket, or to cut the data wire inside the USB cable if youre sure you can identify.
There may be a way to disable mass storage mode, i dont have an A129 so cant check.