Missing Lines

In the attached picture you can see a half-circle but actually, it is a full circle. A few segments of the line are not visible. Could you please tell me how to solve the problem?

Hi @MARUF
You could start by posting the file (just the offending geometry) and also run the Rhino command SystemInfo and paste the result here - that way there’s a chance someone can help you. Could be a video driver issue, but I’m just guessing.
HTH, Jakob