In the file below, there are some “washers” which are simple extruded discs, but on one I put a small fillet on the top outer edge. If I subobject select the upper edge of hole on the filleted one and use the Gumball extrusion ball, the extrusion is not closed. If I select the lower hole edge of that one or either the upper or lower hole edge of the unfilleted one, the extrusion is solid. Therefore the fillet is somehow interfering with things. The normal ExtrudeCrv command extrudes solid.
SO-Extrusion.3dm (3.2 MB)