Sorry for the delay but the thread is a decade old so....
What's the value of the pot in question? Link to actual product or datasheet?

It certainly sounds like a hardware issue. If it works OK with a rorary pot, of the same value, then the slide pot is crap - obviously.

But, do you really NEED 10 bit resolution? Even if you throw away say 3 bits you still have 127 discrete values. On a 70mm long pot that's about 0.5mm movement. If the sim software expects 10bits then just shift the value left three digits.