My son picked up his new s8 a day ago from T-Mobile. We noticed yesterday a line showing up inside the app tray. It comes and goes and is becoming more visible, and consistent, with time. He is also having major issues with his audio when playing music. Songs will stop, re-start and then jump ahead and then re-start again. Obviously, this phone has major software issues. We re-set it and it continues. Sadly, the phone will go back to T-Mobile tomorrow morning. He JUMPed from an iPhone 6s to this and has decided that he will go back to iPhone... which I am sad to see as I know he really likes this phone. But a lack of trust now exists, which I fully understand.
I also JUMPed from an iPhone (7) to the s8. In my case, knock on wood, I have not experienced any issues with mine. It is working exactly as it should. But thought I would pass this along just in case anyone else has this issue...