The vertical two inch board on our shelf was only attached to the horizontal board by about six brads (there were no brads in the middle of the board where the center support is) . The ends of the clothes pole was firmly attached to the wall, but the center of the clothes pole is attached to the middle of the shelf. Our vertical board came loose (off) after going down some oscillating highways (similar to the video of that oscillating suspension bridge in Washington).
I put eight evenly spaced 2" brass screws through the front of the vertical board and now my shelf and clothes pole are very rigid.