Invisible Horizontal Line on Screen

[abigjerk]

So to me this is a rather odd phenomenon:

I have to use CRU with my Samsung RU8000 55" 120 Hz HDTV in order to get my games to run at 1440p rather than at 4K.

I also have the comprehensive user manual for my television and it shows what Pixel Clock, Refresh Rate, and Polarity to use for each respective resolution. But when I use the values the manual insists I must use, I end up with an invisible, horizontal line near the top of the screen. It's only noticeable when I move the mouse arrow over top of the line or I drag a window around the vicinity of the line as well. It's very similar to wheat screen tearing looks like when gaming.

The manual states that if I'm "connecting a computer" to the television for 3840 X 2160 resolution, I need to have my Pixel Clock at 594.000, Refresh Rate at 60.000, and Polarity should be MINUS-MINUS. When I use those values, I get the invisible horizontal line.

The other section of timing tables in the manual are labelled as being for "Video Signals" Within these, they say for 3840 X 2160, Pixel Clock must be 594.000 (same), Refresh Rate 60.000 (again same), but this time the Polarity must be PLUS-PLUS. When I utilize these settings with the two positive polarities, I get no weird line running across the top of my screen.

I have no issues whatsoever with using the 2569 X 1440 resolution no matter what values I insert into CRU with the exception of Refresh Rate. The panel refuses to budge above 120 Hz no matter what wacky timings I try.

So anyways I'm rather curious, why do I get this strange horizontal invisible line running across the top of my screen when I use the timing values the manufacturer insists are correct for my setup?

Any other advice or enlightening knowledge is appreciated. I love your forum and CRU. Thank you so much for your time and dedication.