app crash after add closure what to do??

Gnarly

So I can't replicate but apple rejected my game due to:

"We discovered one or more bugs in your app when reviewed on iPad running iOS 8.1.3 on both Wi-Fi and cellular networks.

Specifically, we noticed the Application will quit upon initial game play and exiting the first Ad that appears."

Its chart boost. I can't replicate it on my iPad. I changed the add position and resubmitted and same thing....

So what would you do?

Is it a chart boost problem? Should I put a rev mob add and try??

thanks