A troubleshooting technique I learned here on the forum is to use pieces of electrical tape to cover the suspect portions of the center rail. Be sure to cover the side of the rail, where the backside if the wheels likely touch or arc to the center rail. (Where your arrows are)
If that works, without interfering with the center roller contact, you are all set. Otherwise you might carefully adjust the center rails inward, toward each other, to open the gap for the wheels to pass through, without using the tape on the center rail.
Hope that helps.
Will
