Contour Line for z-fighting faces

The contour lines of fully contacting faces are not drawn.

For example, if you create a plane and then create a smaller plane on top of it, the contour lines are visible immediately after creation. However, when you move the smaller plane using the 'snap faces', the contour lines often disappear. It seems they are being treated as occluded.

When importing external files that were not created in Blender, many objects exhibit this issue. Since I am working in a time-constrained environment, it is difficult to fix them one by one. I would like to ask if it would be possible to ensure that contour lines are always drawn for such objects as well.

Fixing the existing behavior would be appreciated, but alternatively, it would also be helpful to have a separate option for handling these kinds of Z-fighting objects.