When I turn the power on on my Neff T4243 and select a hob, all four hob indicators start flashing E and a beep sounds for about 15 seconds. If i then turn it off then on again it works fine. A few minutes later with power off it will fail again. I have tried entering childlock mode and coming out again but this doesn’t cure it and I’ve tried it with the hob perfectly clean and no metal or other objects on or near the hob. How annoying! Any ideas please