I'd prefer not to call it the "Sl....ry Ni....ple" , but that said, I had the same problem on my old TP600x. I'd let it drift and pull it back and drift and pull back and drift, etc... You get the idea. It would slow down or stop after a few repetitions. I never figured out why it was happening, but it never really bothered me that much either.

One thing I can say is that I never liked that d*mned thing in the middle of my keyboard in any instance. I definitely prefer a mouse and/or a trackpad of some form.