Possible to fix off-center rotary stick?

[Damfino]

OK, the subject title isn't very descriptive. The situation is, I just build my first control panel (basically a test run for a MAME cabinet later in the year), using an ipac VE, Druin's rotary interface, and Happ rotary joysticks and buttons from Ponyboy.

One rotary joystick works perfectly - the other is "off center" so that, when it's not being touched, it just barely activates the "up" microswitch. (Of course, I didn't notice until I had mounted it...) If I push the stick down just a tiny bit, I can get it to not hit anything, but as soon as I let go, it clicks "up" again. I took the shaft out and took a peek but I don't see any way to really adjust these things. I redid this a couple times to make sure I wasn't putting anything together wrong... but it's just like the other stick that is fine. For now, I removed the one and just stuck in an extra competition stick I also ordered.

So if there any way to tweak the center of these? Or will I need to exchange it for another?

Thanks!