Nittaku Super Training

I paid $59.95 at paddle palace for 120 nittaku super training balls. I had the these balls stored for a few months. Then when I opened the plastic bag to get the balls, they started exploding, those that didn't explode without touching them, they exploded on first bounce. I also had boxes of DHS balls that does not have this problem, and were stored in the same area with those nittaku super training balls, which is about 78 degrees fahrenheit. By the way, when I told paddlepalace about this problem, they didn't give me any refund for the defective merchandise they sold me. Beware.