I can confirm this issue is confined to the display board itself...as other LED displays operate fine on the machine.
From what I can ascertain there is a some kind of row clocking error happening. I have 3 LED boards exhibiting this behavior. 2 boards are REV C while another is REV A none have any modifications or factory mods. all board behave identically in every machine they have been tested in. it's been so long that I don't recall if these boards worked for a period of time then ceased... but i do recall one display acting this way out of the box and we just went ahead and used it until the machine came back to our shop for service.
in any case, a graphic pixel meant to be drawn in (for example) the 3rd row is instead being drawn in the 2nd row...with a partially illuminated "ghost pixel" in the proper location directly below it in the 3rd row as it should be... as if there is some kind of problem in the clock signal making the row clock earlier than expected but also when it should.
as you can see in the attached pictures, the top row of pixels of the letter T in "TEST" should be 6 pixels from the bottom of the display, but it begins drawing them 7 with the partially illuminated "Ghost pixels" showing up at the proper row. as well as a display test with a horizontal line and it's accompanying "ghost" pixels below in what i'm to assume the proper space. (cannot verify since I can't just illuminate one specific line but other evidence suggests this)
the "ghost pixels" illuminate at about 60% intensity.
the image is perfectly static. it does not fluctuate or jitter... at least visibly to me anyway. I'm unsure if it has perfect frames and imperfect frames regularly interlaced or if it's a constant row by row issue.