Please allow Stroke Size <1.0 in Layer Styles

Video is pixels, and 1 pixel is the minimum size of a pixel. If a 1-pixel wide stroke is not perfectly aligned with the pixel grid, you get a 2-pixel wide color that is a percentage of the original color. If the line moves slowly, you get flickering colors unless you turn off antialiasing. If you do that, you get a line that changes width as it moves. Because you are dealing with pixels and not vectors, there is no practical reason for a stroke that is less than 1 pixel wide, and there is no way to accurately display that thin line in a pixel-based format like video.