One thing that may or may not be. The teeth on the tedder look like they are swept back a little. It could be due to usage over time the teeth have bent over time swept back, or it could be just the way it is. I went and looked at our Kuhn and the teeth are more straight up and down. The swept back would seem to me to not lift the hay as much as if they were straighter. I would buy a new tooth and see how they compare length and angle wise to the older teeth on yours.
Things I have found that affect the way a tedder works, some have already been talked about. Swath width, how heavy the hay is, length of the hay, if the tedder is matched to the width or the mower. Ground speed, PTO speed, angle of the baskets, tires.
One thing we have done in really heavy hay is 1st time tedd normal with the rows. The next day tedd across the rows, this will help sometimes break up some of the clumps.
The other things is what are you mowing with? If you are using a haybine, they can sometime "drag" hay or have a area where hay hangs up, then drops, over an over creating clumps in the swaths, then the tedder hits these and can break them up. Is your mower leaving even swaths?
Withour seeing 1st hand, its hard to say for sure. Hope this helps.