Ordering glitches when far away from camera?

I have a textured mesh where every vertex has y == 0, and a camera looking straight down at it.
I also have a LineRenderer that I use to draw on top of the mesh in solid color (e.g. to outline a part of the mesh). For the LineRenderer, I set every line vertex to have e.g. y == 1.
All is good when the camera is relatively close to the mesh; however, when the camera is some distance away, the lines reliably “jump” under the mesh - I can see them properly only thru the transparent holes in the mesh texture. The jump is not gradual, as I move the camera very slowly at some point the lines just “disappear”/“reappear”.
Is this a bug of some sort? Is there a better way to enforce ordering of what’s visible in this case?

What you’re describing sounds like a case of Z-fighting. Try increasing the distance between the linerenderer and the mesh, increasing your camera’s near clip plane, or reducing its far clip plane.

I think @tanoshimi is on the right track. An alternate solution would be to use a material/shader that doesn’t do depth testing. That way the line will always appear on top. Also, if this is going on far from the origin (like the camera position has elements in the thousands… then floating point precision issues will creep into everything causing jitters and whatnot.