Cit --
I had that problem develop on my 13 month old CH rudders, and it wasn't a small fluctuation. I'd see both centering drift of several hundred points, and lots of spiking. (My X52 has been rock solid...go figure.) Anyway, one really good thing about the CH stuff is that the potentiometers can be purchased separately for $5 or so.
I didnt even do that -- I opened up the pedals, and switched the potentiometer for the brake with the one for the sliding rudder input. Since the brake "centers" with the pot at full deflection, it completely avoids the defective center region. And the pot from the brake centers just fine.
Though I'd never claim to be an expert, I'd bet you're looking at a pot on the way out.