(I assume that your box is meant to have a curved cut-out
).
As it's just the lines disappearing, it shows that it's your graphics card/drivers that are having a problem with the lines.
I have seen similar to this on a laptop we have here. That also has Intel graphics and it has trouble clipping lines to the left of the view e.g. if the green bounding box goes off the left edge, rather than being clipped correctly, it draws a green line between the top and bottom along the very edge of the window. This is certainly a driver problem.