IOS game version crash alternately when getting notification on device

Hi,

Sometime when getting a notification (tried with some different ones - SMS, Facebook chat, whatsapp, etc) - the game crashes.
Using AdMob and google play services. Xcode 7.2, unity 5.3.1
Test with several devices and IOS versions, all the same. Android works great.
Appreciate your advice.
Thanks!

Crash Logs:
--------------------------------------
Thread 0 name: main Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0 <myapp> 0x000000010009905c...

IOS game version crash alternately when getting notification on device