Welcome to the forums! Do you notice any places where there may be bends in the frame, say from lawn mower throwing rocks, etc? If lubricating the slide area didn't help, try white lube. WD40 as well as penetrating oils will dissipate after a while, but white lube will remain. It is the same stuff car door hinges are lubricated with.

You need to install the sill part of the patio frame directly onto the concrete slab because it is the proper way. Before you install you should check the level between concrete slab and frame. Still any que. feel free to ask.

Thanx Henrykemp1, I was thinking of laying a thin layer of foam, then secure a 2 x 8 using tapcon screws, then installing the patio door frame....I went last nite to the local Home depot and the guy said I did not need to screw the sill part of the frame down because the screws securing the frame by the sides is sufficient. In my books, I would think that a couple of screws in the sill should do. ANy comments - thanx