I thought same but how explain this :

If I revolve the curve.
Save, exit, reopen and shell the surface, you don't have the problem...

 

So I think the shell on the revolving has a problem.
Perhaps a rest of history ?

Michael, could you test and see if this experience is same for you ?

Left a curve is revolved then shelled.

Right a curve has been revolved then saved, exit of Moi, reenter Moi reopen file and shelled the surface.
See the center of inside render indicating the problem.