There seems to be something wrong with the display function on my Galaxy S5. The Smart stay function also does not work. When I switch the phone on in the morning, it immediately goes black and I have to reset the screen timeout again to 2 minutes. Yesterday it went to 10 minutes at some point, then later reverted to zero. I contacted Samsung who recommended a factory reset. Tried that. Made no difference. And so I arranged to return phone to supplier to receive a new one. Received new phone. Same problem. Seems to happen at random.