One of two things happened, probably with each of these.

-1-did either of you leave the balls in the trunk of your car then just go in and throw it? The extreme heat then the beating on the lanes could be the cause.

-2-you should consult the houses where you guys bowled. They should replace them (not sure about the Mutant since it was used). The ball more than likely hit something that caused them to crack.

I have a Voo Doo and a Mutant (used to have 2 them). I put alot of games on them and none have cracked.

You can always drop a call to Track. They have great customer service and may be able to do something for you.

Goodluck