I have a 8' multi-window slider. It has always been kind of loud but recently it is extremely difficult to open. We removed the doors and cleaned the track and sprayed it w/ silicone. It worked but not great or smooth. Within a week I was right back where I started. The wheels look operable but I am thinking that is my next step. When we removed the door, we removed 2 screws on the sides at the bottom but it didn't appear to do anything. We don't know how to remove the wheels. Can anyone help?