Facing serious problem after changing player settings in iOS

Dear Moderator ,

We are developing promising game using your kit.

We have arranged 80 fights in story mode and 16 fight in battle mode.

Game was working well till we tried to upload to Apple app store.

At the time of upload we found that we need to select following value to support standard architecture.

PlayerSetting->ScriptingBackend->"IL2CPP" && Architecture->Universal

Prior it was
PlayerSetting->ScriptingBackend->Mono (2.x)

After triggering option we produce build.

We found serious issue  which can not allow us to upload game.

AI stops after each 2-3 fight during the fight and game crashes frequently as well.

We can say frankly that no user can play at least 3 fight consequently.

We have spent 8 months to develop this game with fantastic graphics and stable AI.

We are helpless now as we do not know what issue is causing frequent crash and stops AI from working during the game.

I can send you iOS build after including your  udid .

You can watch game video on our offical fb page as well.

https://www.facebook.com/motionartgames/

Its taken from iOS device.

Note:

If we changes option PlayerSetting->ScriptingBackend->Mono (2.x) again we are able to play at least 8-10 fight.

But this option will not work now as apple will not allow to upload.