I purchased a new rear cup holder as the old one broke. I removed the screw on each side and was able to remove the old part. I slid the new part onto the two rails but the it won't slide closed. When pushing it into the opening, the top center of the cup holder gets stuck when it hits the rails in the top center of the opening. I've manually compressed the mechanism on the sliding part but it doesn't make any difference. What's the trick?