I have this exact same issue.
My Rival's mouse feet seem to be unbalanced.
Only three of my mouse feet actually touch my mouse pad, the fourth mouse foot (located under the left click button) doesn't touch the mouse pad.
I even tried replacing the original mouse feet with a replacement set, and the imbalance is still present.
I'm hoping that eventually the three feet which touch the mouse pad might be worn down enough so that the fourth foot eventually makes contact.
It's frustrating having my mouse dip down off balance every time I use the left click button.
Edited by minipman - 3/30/14 at 3:14am