W-d40 is great stuff but it gets under dirt, grime and grease to clean that area.
I would pull the rack out and flip it on it's side and greese up the movmentfor the rack
I like a Industrial Grease that seam to work good for me .
I guess I am going to have to pull out the entire mechanism to get at the mechanical parts buried in the wall.
The number of screws and parts on top of parts is discouraging.... but no worse than replacing stuff under the hood of my PT cruiser!