So as I mentioned earlier, I took some time to really examine the cover and identify the problem. I have successfully fixed my clicking cover, and I hope that everyone else will be able to as well.
First, the problem comes from the horizontal piece of metal that runs the length of the underside of the cover. The piece of metal holds the tabs that you slide into the front end of your macbook, not the two larger tabs that lock in towards the middle.
If you look at the piece of metal that runs the length of the cover, you'll notice that it sits on the curvature of the metal. Because of this, a small variation in placement can have an effect on the vertical positioning of the clamps. If the piece is too far up the curvature, you'll get the clicking sound. If the piece is too far back, you'll get the sliding cover as demonstrated in the youtube video.
While I don't think it would be possible to fix the sliding covers without a new cover entirely, it is possible to fix the clicking case. Simply take a small pliers and bend the tab (on whatever side is clicking...) toward the end of the cover nearest it. Essentially bend the tab down slightly. The entire metal piece should move inward even more, which creates pressure in the case. In fact, this is how it was supposed to be originally.
I hope that's clear enough. Just bend the tab down ever-so-slightly. If you bend it too much, just push it back up, but be careful not to tear off the side of the metallic piece.
After a minute or two of tweaking, I managed to make my cover free of the annoying click when you pick it up or set it down.
I hope these instructions were clear enough. If you have any questions, let me know. Hope this helps.
By the way, bending all of the tabs will eliminate some of the sliding, but it is not a permanent fix. Still, if you only have slight movement, adjusting all of the tabs will allow for a tighter fit and will eliminate some of the movement.
Also, can you guys post pictures of the underside of your cases? Especially the YouTube guy with the major movement. I'm curious to see how the underside of the cases compare.