Ghost lines appear in extruded geometry

[Anonymous]

After drawing lines/arcs, joining and then extruding, phantom lines appear in the geometry in Model space.

They shift/disappear/reappear sporadically as I pan and zoom. Seems to only effect shallow extrusions (1/4" lauan material).

Any way to fix this? Using AutoCAD Mac 2015.

[nestly2]

I tend to see similar when there's non-continuity in the geometry, usually due to non-planar surfaces/faces.   If you can attach a sample drawing, we might be able to tell if it's just a display issue, or if it's caused by a problem with the geometry. 

BTW, at this point it's unclear if it matters, but there is a separate forum for AutoCAD for Mac

[Anonymous]

Thanks Nestly,

Attaching a screen grab showing the lines. Again, this is a very simple extrusion – not sure what the problem could be. 

I'll re-post in the Mac form as well – thanks!