Reply to Traktor Scratch Pro, only one deck working properly

I use Scratch Pro with vinyl, and only one deck seems to work properly.

The left deck seems to often get stuck on this setting, and it's impossible to click to the icon on the right.

http://i.imgur.com/oyCLGHx.png

The track plays but doesn't respond well to the deck, so if I pull the vinyl back it speeds the deck up.

Any ideas what's going on? I've swapped needles on both decks in case that was the problem but it still only happens on the left deck.

Any help much appreciated.