I had a Danger Zone that I used for a couple of months, put it in the locker at the center, and when I next went to use it after the summer off, it was cracked all the way around the ball. The center was open for the summer so it was somewhat temperature controlled, and that was before I started cleaning the balls in hot water. Brunswick replaced the ball with no problems.
I had another ball, the Omega LM, that I used extensively one season, put it in my closet, and when I pulled it out for the next season, it had cracked all the way round the ball. It was sitting in my bowling bag so I did not notice the crack until I removed it at the center.
I would also be curious to find out why this happens only to some balls.