Reply to vci-100 left jogwheel won't respond

I have a problem. I'm using the vci-100, w/1.3 firmware on traktor 3.4 (mac 10.4.11, Dual 2.0 G5, 3G ram) and my jogwheel on Deck A is acting up again.

The left jogwheel (deck A) will not respond as well as the right jogwheel (deck B) More specifically, when I touch both, the LED will turn red on both, but when there are tracks loaded, the one on the left will not "scratch" the track forward or backward, regardless of how much I spin the jogwheel. The one on the left works correctly.

What is wrong, and how do I fix it? It's the second time that this has happened. the first fix involved playing w/the rear sensitivity adjustment (and unscrewing the faulty jogwheel), but I don't use it daily or even weekly, so I can't say that overuse causes it. I don't believe that I should be tweaking the knob/unscrewing the jogwheel every time I use it.

Any suggestions?