[andyg]

Have you fitted any aftermarket kit, like a DAB radio or dashcam for example? If they are connected to a 12v permanent live feed then even the smallest thing can drain enough to confuse the battery sensor and the stop/start charging status. That happened to me with an aftermarket DAB adapter until I changed it to a 12v supply that was switched on/off with the ignition. It sounds like you are very tech savvy and will already have thought of this, but I mention my own small mistake just in case it helps.