ArrowPointer will not draw for some directions

[Crzyrndm]

As the title says, while using the ArrowPointer objects, some directions are absolutely refusing to draw. The only thing changing is the direction the arrow is being drawn in.

Vector3 dir = Vector3.ProjectOnPlane(thisVessel.srf_velocity, planetUp).normalized;
if (pointer == null)
    pointer = ArrowPointer.Create(thisVessel.rootPart.transform, Vector3.zero, dir, 100, Color.red, true);
else
    pointer.Direction = dir;

If I spin a vessel in a circle (Aeris 3A on the grass next to the runway) running the above code, between a heading of 30 and 150 the pointer will not be visible.

Anyone know why this might be?