Problems was caused by angle=2*pi and steps=2 in screw modifier. Such configuration produced duplicated geometry to close object and it was confusing for subsurf cache. Restrict steps=2 for screw modifier now, so now 3<=steps<=512.
Problems was caused by angle=2*pi and steps=2 in screw modifier. Such configuration produced duplicated geometry to close object and it was confusing for subsurf cache. Restrict steps=2 for screw modifier now, so now 3<=steps<=512.