Strip pattern on the TV screen - What kind of defect could it be?

I bought a LG 42LW4500 TV used about a year ago. It is a 1080p 3D device. There were no problems all year round, but now all at once I see black stripes through the whole picture at regular intervals. There's no defect in the HDMI device, because the stripes are also visible when I'm about in the TV menu and no Gerär (about PS4) is active. Any experiences with such a defect? The defect first appeared half an hour ago.

Turn off the device and disconnect the power plug from the wall outlet.

Wait two minutes before plugging the power cord back into the wall outlet.

Plug the power cord back into the wall socket and turn on the TV to check its operating status.

If the problem can't be solved with the above steps, a repair may be necessary.