Samsung TXK2754 27" TV "sound bars smart" Questions

...sound. When we switch it off there is a horizontal white bar that flashes on the screen for a second. I would like to fix it as the TV has been great so far. Please help! RELACED THE VERTICAL OUTPUT ...

Smart TV I pruchased this TV 3 years ago . It worked great until a couple months ago. The picture is clear, the sound is great, it does hesitate to come on when I first turn it on; however, now, there