I have recently become aware (bothered by) what appears to be
a line moving up across the TV screen. The TV is a Samsung
4K with HDMI input, and the line that moves up the screen
appears to be a missing scan line.

The TV derives its input from a linux computer running
mplayer, and the video card is an NVidia 610. The
HDMI output goes to the TV and the vga output goes to
a monitor which I can see while the TV is playing.

The discontinuity on the TV screen is not replicated
on the monitor screen.

The moving line appears every few minutes.

I was not conscious of the problem prior to a shutdown
of the video server to increase the storage capacity.

Any suggestion of what might cause the effect, or questions
that may further clarify the phenomenon would be appreciated.