What would cause throttle jitter in only one direction?

Got a Saitek X45. Love the thing, and there's nothing I'd want to replace it with for less than $500. The throttle developed a big dead spot right in the middle of travel. Disassembled it and blew it out with compressed air. That made it much better - the dead spot worked, but jittered a lot. So I took it apart again and went after the sensor with contact cleaner.

Now, if you bring it slowly down from full throttle, it's completely smooth. But if you bring it slowly up from idle, there's a big dead spot from about 25% travel to 75% travel. After that it works fine. If, for instance, I set the throttle in the middle, the sim thinks I'm at idle. If I pull the throttle back very slightly, the sim sees the correct throttle setting.

So it works great in one direction, and has a giant dead spot in the other. I'm at the end of my electronics repair knowledge, and would have thought it'd either be dead in both directions, or alive in both directions. So what's going on here, and is there any hope for this old thing?