Horizontal line in the middle of the LG UHD screen

Since a day or two there is a horizontal line showing in my TV (LCD UHD 49SK8500PLA). It shows on HDMI as well as the build in Netflix app.

At the moment TV is started the horizonal line is not yet visible, but it appears after 5 seconds or so and stay present. The firmware is up to date.

What's going on? Is it a software issue or some other major issue?