It's acting "correctly", it just turns out that I tend to move my mouse around the center of the card while I'm reading it, which makes it super obnoxious.
Actually, I just played with it some more, and you know what it is? My brain knows the mouse is controlling it, so while reading, I'm unconsciously trying to find a middle spot to put the mouse in a vain attempt to make it sit flat, which has the effect of causing nonstop wobbling.
It's like it's designed to irritate me. :D
