4k running so smooth

I was able to try silent hunter and was able to play any thing in 4k once but when I stop and try another movie it plays but all black with some pixeling not sure why like it has problems displaying it.
Have to power off and then power on and go back in to get something to play once but will only display proper on first try any suggestions
 
I went into display and set it to 4K2K-60hz and same issue able to watch anything 4K once but once I edit and try again the screen is pixellated and black and just audio comes in.
Is that what you guys have it set to.
 
if you dont youll get one black line on top and no move but sound if that what your asking and it should stay at that sometime will go back and need do it again
 
if you dont youll get one black line on top and no move but sound if that what your asking and it should stay at that sometime will go back and need do it again

Thanks Marley for the suggestions i did notice it likes to jump back to 720P-60hz on its own quite often.
just curious what you have it set to in display i have it set to 4K2K-60hz because thats what my sony TV is but notice a few different options for 4k2k with different hz in the display setting?
TIA