I've just picked up a DC25 Animal, on which the ball constantly jams. The ball can be rotated by hand, although it 'catches' and feels as though it's fouling on something. When the cleaner is pushed across the floor the ball won't move at all. I'd like to sort this out, as the cleaner is in otherwise decent condition, and I'd like to get it working properly. Before I get the tool box out, does anyone know if this is a known problem, and if so, what I should be looking for?