Heater Control Up - Down

[Furry Dice]

The lower heater wheel that control the air up or down will now only move from the middle to the left, so now I can't shut of air to the footwells.
This has only happened in the last couple of days, I'm guessing maybe something has got stuck in the flap and is stopping it. Anyone any ideas, don't really want to take the dash out if I can help it. Cheers in advance