Probably the mechanical resistance of the pot. Some early Spoiler, Distillate and Epic pots were loose feeling because they couldn't put the plastic wave washer in the pot.
One thing you can try is a felt washer between the knob and the top of the guitar. You can vary the thickness until you file the right feel. It can scrub the finish under the knob or knob skirt some, but if you're never using a smaller knob no big deal.
Of course, you can replace the pots with ones that have more mechanical resistance too.
