I have a 2013 Defender XS with a factory fitted heated windscreen which doesn’t work properly. When l put it on, it only partially de-mists the screen, l get uneven vertical lines across the screen and on the passenger site there is a 300mm area that doesn’t de-mist. The screen looks ok and isn’t damaged, the connections to the screen are ok and the relays, fuses all seem to be good. I don’t know what else to do other than change the windscreen. Has anyone one had the same fault and how was it resolved?