Question: Can a burn pot that is cracked or warped still be used?
Answer: Yes. A burn pot has two main functions. 1) It holds the pellet fuel in place while it burns, and 2) It allows airflow to come up through the holes in the bottom to feed the fire oxygen. As long as a burn pot is still performing these functions, it is still usable.
Exceptions would be if pellets are falling through the cracks, or if warping of the pot is causing gaps to form around the burn pot's perimeter, which will affect the way air flows through the pellets.