Ken, I think I've narrowed the problem to condensate pooling in the lower track. Since the metal is much more exposed on the outside it conducts the cold and freezes. I'm afraid the continued use of salt will cause excessive corrosion, although that's what I used on the original HFGH door. The door seems to ride exclusively on the rail, on the nylon wheels so I'm thinking I can drill holes through the flat portion of the metal and a cross hole in to the wooden sill plate from the inside. The WD40 did help with freezing condensation on the door jam and upper guide.
