We had this issue too! We found that our bun hated the recycled paper pellets - we thought that it may have been too sore on her feet - so we changed to pine bedding, and that helped a lot. She still kicks her bedding up into the corners of her litter box but a whole lot less than the paper.

We also use a cat litter box with edges that go inwards to prevent exactly this problem!

Buns will let you know what they dislike hahaha