Reply to fader problems

hello,
i have a bit of a problem with my left fader of my vci-100se, when i glide it up to 100%, traktor goes a bit crazy and he gives my values on the screen like 50%,40%,60%. if i move my fader just a tiny bit down, then it goes well and i get the 99% fader volume in traktor

is this because their is a bit of dust in de fader or is it another problem?
all help would be great