Apple rejected my app due to crash on load and I can't reproduce it. What should I do?

My app was rejected to a crash on launch. But tried to run it on a device by installing the app via itunes and testflight, I also implemented crashlytics in my app, but still I can't find the source of crash. What should I do?

We found your app crashed on launch so we were unable to review it.

Please revise your app and test it on a device to ensure it will launch without crashing, and that it runs as expected, before resubmitting.

Please see the attached crash logs.

For discrete code-level questions, you may wish to consult with Apple Developer Technical Support. If you have crash logs, symbolicate the crash logs before contacting Apple Developer Technical Support.

If you have difficulty reproducing this issue, please try testing the workflow as described in Testing Workflow with Xcode's Archive feature.

EDIT: I tried to symbolicate the crash log and I saw that it crashes on thread 0 index 0 which is the getAllContacts function. I'm not sure what's the problem. here's the code:

- (NSMutableArray *)getAllContacts{
    ABAddressBookRef addressBook = ABAddressBookCreate( );
    CFArrayRef allPeople = ABAddressBookCopyArrayOfAllPeople( addressBook );
    CFIndex nPeople = ABAddressBookGetPersonCount( addressBook );
    NSMutableArray *contact = [[NSMutableArray alloc] init];

    for ( int i = 0; i < nPeople; i++ )
    {
        ABRecordRef ref = CFArrayGetValueAtIndex( allPeople, i );
        NSString *firstName = CFBridgingRelease(ABRecordCopyValue(ref, kABPersonFirstNameProperty));
        NSString *lastName = CFBridgingRelease(ABRecordCopyValue(ref, kABPersonLastNameProperty));

        if(lastName == nil && firstName != nil){
            [contact addObject:[NSString stringWithFormat:@"%@", firstName]];
        }
        else if(lastName != nil && firstName == nil){
            [contact addObject:[NSString stringWithFormat:@"%@", lastName]];
        }
        else{
            [contact addObject:[NSString stringWithFormat:@"%@ %@", firstName, lastName]];
        }
    }
    CFRelease(addressBook);
    CFRelease(allPeople);
    NSLog(@"All Contacts: %@", contact);
    return contact;
}

Here is the crash log after symbolication:

{"bundleID":"com.axon.undotext","app_name":"Undo Text","bug_type":"109","name":"Undo Text","os_version":"iPhone OS 7.1.1 (11D201)","version":"1.5 (1.0)"}
Incident Identifier: CDEE9887-DE46-4C7B-93D9-6F5B64C30448
CrashReporter Key:   814350e202fe6bd49117983388396d3d1b870da1
Hardware Model:      xxx
Process:             Undo Text [3268]
Path:                /var/mobile/Applications/1F7938ED-7911-4838-8F79-26039EF3E386/Undo Text.app/Undo Text
Identifier:          com.axon.undotext
Version:             1.5 (1.0)
Code Type:           ARM (Native)
Parent Process:      launchd [1]

Date/Time:           2014-06-12 13:43:03.567 -0700
OS Version:          iOS 7.1.1 (11D201)
Report Version:      104

Exception Type:  EXC_BREAKPOINT (SIGTRAP)
Exception Codes: 0x0000000000000001, 0x000000000000defe
Triggered by Thread:  0

Thread 0 name:  Dispatch queue: com.apple.main-thread
Thread 0 Crashed:
0   CoreFoundation                  0x2eb0b3c5 CFRelease + 1137
1   Undo Text                       0x00035897 -[ContactsManager getAllContacts] (ContactsManager.m:58)
2   Undo Text                       0x00028d59 -[ViewController setupView] (ViewController.m:123)
3   Undo Text                       0x00028901 -[ViewController viewDidLoad] (ViewController.m:65)
4   UIKit                           0x3140ea4f -[UIViewController loadViewIfRequired] + 515
5   UIKit                           0x3140e80d -[UIViewController view] + 21
6   UIKit                           0x31485c39 -[UIClientRotationContext initWithClient:toOrientation:duration:andWindow:] + 385
7   UIKit                           0x3148459d -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:isRotating:] + 1197
8   UIKit                           0x314840e3 -[UIWindow _setRotatableClient:toOrientation:updateStatusBar:duration:force:] + 43
9   UIKit                           0x3148406b -[UIWindow _setRotatableViewOrientation:updateStatusBar:duration:force:] + 91
10  UIKit                           0x31484003 -[UIWindow _setRotatableViewOrientation:duration:force:] + 39
11  UIKit                           0x3147c67d __57-[UIWindow _updateToInterfaceOrientation:duration:force:]_block_invoke + 105
12  UIKit                           0x31410695 -[UIWindow _updateToInterfaceOrientation:duration:force:] + 381
13  UIKit                           0x31483d55 -[UIWindow setAutorotates:forceUpdateInterfaceOrientation:] + 693
14  UIKit                           0x31483825 -[UIViewController _tryBecomeRootViewControllerInWindow:] + 157
15  UIKit                           0x31415611 -[UIWindow addRootViewControllerViewIfPossible] + 457
16  UIKit                           0x31412dd5 -[UIWindow _setHidden:forced:] + 301
17  UIKit                           0x3147ca4d -[UIWindow makeKeyAndVisible] + 57
18  UIKit                           0x314796e1 -[UIApplication _callInitializationDelegatesForURL:payload:suspended:] + 1817
19  UIKit                           0x31473cc5 -[UIApplication _runWithURL:payload:launchOrientation:statusBarStyle:statusBarHidden:] + 717
20  UIKit                           0x3140fc93 -[UIApplication handleEvent:withNewEvent:] + 3547
21  UIKit                           0x3140edf5 -[UIApplication sendEvent:] + 69
22  UIKit                           0x31473401 _UIApplicationHandleEvent + 613
23  GraphicsServices                0x33a46b53 _PurpleEventCallback + 607
24  GraphicsServices                0x33a4673b PurpleEventCallback + 31
25  CoreFoundation                  0x2eba5845 __CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE1_PERFORM_FUNCTION__ + 33
26  CoreFoundation                  0x2eba57df __CFRunLoopDoSource1 + 343
27  CoreFoundation                  0x2eba3fab __CFRunLoopRun + 1403
28  CoreFoundation                  0x2eb0e765 CFRunLoopRunSpecific + 521
29  CoreFoundation                  0x2eb0e547 CFRunLoopRunInMode + 103
30  UIKit                           0x31472627 -[UIApplication _run] + 759
31  UIKit                           0x3146d88d UIApplicationMain + 1133
32  Undo Text                       0x0004deff main (main.m:16)
33  Undo Text                       0x00027764 start + 36

Thread 1 name:  Dispatch queue: com.apple.libdispatch-manager
Thread 1:
0   libsystem_kernel.dylib          0x39d52804 kevent64 + 24
1   libdispatch.dylib               0x39ca1051 _dispatch_mgr_invoke + 229
2   libdispatch.dylib               0x39c9b2df _dispatch_mgr_thread + 35

Thread 2:
0   libsystem_kernel.dylib          0x39d65c70 __workq_kernreturn + 8
1   libsystem_pthread.dylib         0x39dcac1f _pthread_wqthread + 307
2   libsystem_pthread.dylib         0x39dcaad8 start_wqthread + 4

Thread 3:
0   libsystem_kernel.dylib          0x39d65c70 __workq_kernreturn + 8
1   libsystem_pthread.dylib         0x39dcac1f _pthread_wqthread + 307
2   libsystem_pthread.dylib         0x39dcaad8 start_wqthread + 4

Thread 0 crashed with ARM Thread State (32-bit):
    r0: 0x00000000    r1: 0x39f720f8      r2: 0x00000003      r3: 0x00000002
    r4: 0x00000000    r5: 0x16e85070      r6: 0x00000000      r7: 0x00177300
    r8: 0x00000144    r9: 0x3ba52e30     r10: 0x16e69890     r11: 0x31a3841a
    ip: 0x2eb0af55    sp: 0x001772c0      lr: 0x0003589b      pc: 0x2eb0b3c4
  cpsr: 0x60000030

Looks like your app is crashing while rotating, are you sure you properly tested this? Especially starting your app while device is in landscape vs portrait.

Also something that can induce weird behaviors is starting an app with device rotated BUT with orientation locked.

And test on an actual device, not simulator, in rare cases you have different behaviors.

Also as others stated, learn to symbolicate, that would give you exact line where your code is crashing.