UIDocument saveToUrl Delayed Crash - ios

Question

I have a Core Data app that's been running fine for over 4 years. Last week I updated XCode to version 8.2.1 (can't remember what I was running before this, but it had been months since I updated it).
After updating, I'm now getting a crash that I can't track down. There's a delay between doing something in the app, and getting the crash to occur. I have attempted to setup global breakpoints to gain more information, but nothing specific is shown that I can tell.
I don't explicitly spawn any threads myself.
When my app first launches, in the viewDidLoad of my initial viewController I do this:
- (void)viewDidLoad
{
[super viewDidLoad];
NSFileManager* fileManager = [NSFileManager defaultManager];
NSURL* ubiquitousURL = [fileManager URLForUbiquityContainerIdentifier:nil];
NSDictionary* localOptions = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],
NSMigratePersistentStoresAutomaticallyOption,
[NSNumber numberWithBool:YES],
NSInferMappingModelAutomaticallyOption,
nil];
NSURL* localURL = [fileManager URLForDirectory:NSDocumentDirectory
inDomain:NSUserDomainMask
appropriateForURL:nil
create:NO
error:nil];
NSURL* localCoreDataURL = [localURL URLByAppendingPathComponent:#"MyData"];
self.database = [[UIManagedDocument alloc] initWithFileURL:localCoreDataURL];
self.database.persistentStoreOptions = localOptions;
if( [fileManager fileExistsAtPath:[localCoreDataURL path]] )
{
[self.database openWithCompletionHandler: ^(BOOL success) {
//log statement
}];
}
else
{
NSFileCoordinator* coordinator = [[NSFileCoordinator alloc] initWithFilePresenter:nil];
[coordinator coordinateWritingItemAtURL:ubiquitousURL
options:NSFileCoordinatorWritingForDeleting
error:nil
byAccessor:^(NSURL *newURL) {
[[NSFileManager defaultManager] removeItemAtURL:newURL error:nil];
}];
[self.database saveToURL:localCoreDataURL
forSaveOperation:UIDocumentSaveForCreating
completionHandler:^(BOOL success) {
//log statement
}];
}
}
Later in the app, I allow the user to create some data and save it (create a new entity), like this:
NSManagedObjectContext* context = database.managedObjectContext;
NSError* error = nil;
if( ![context save:&error])
{
[AppUtility printNsError:error];
[NSException raise:NSInternalInconsistencyException format:#"An error occurred when saving context: %#",[error localizedDescription]];
}
else
{
if (![[context parentContext] save:&error])
{
NSLog(#"Error Saving Parent Data %#, %#", error, [error userInfo]);
}
}
The app will then run for 15 to 20 seconds, then suddenly crash. There is an error in the log that says
[NSError retain]: message sent to deallocated instance 0x608000443b10
And the output in the debug navigator looks like this:
Thread 1 Queue: com.apple.main-thread
0 __forwarding__
1 _forwarding_prep_0__
2 -[UIDocument saveToURL:forSaveOperation:completionHandler:
3 __55-[UIDocument _saveUnsavedChangesWithCompletionHandler:)_block_invoke_2
4 _dispatch_call_block_and_release
5 _dispatch_client_callout ()
6 _dispatch_main_queue_callback_4CF
7 __CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__
8 __CFRunLoopRun
9 CFRunLoopRunSpecific
10 GSEventRunModal
11 UIApplicationMain
12 main
13 start
14 start
Enqueued from UIDocument File Access (Thread 5)
0 _dispatch_queue_push
1 __55-[UIDocument _saveUnsavedChangesWithCompletionHandler:]_block_invoke
2 _dispatch_call_block_and_release
...
Equeued from com.apple.main-thread (Thread 1)
0 _dispatch_queue_push
1 -[UIDocument _saveUnsavedChangesWithCompletionHandler:]
2 -[UIDocument _autosaveWithCompletionHandler:]
3 +[UIDocument _autosavingTimerDidFireSoContinue:]
4 __NSFireTimer ()
5 __CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__
...
In an attempt to get more information, I enabled Zombie settings, then ran this in XCode:
command script import lldb.macosx.heap
malloc_info --stack-history *memory address*
The output of that didn't seem to point to a specific line in my app:
(lldb) malloc_info --stack-history 0x60820f611fd0
0x000060820f611fd0: malloc( 48) -> 0x60820f611fd0
_NSZombie_NSError stack[0]: addr = 0x60820f611fd0, type=malloc, frames:
[0] 0x000000010ffcb130 libsystem_malloc.dylib`calloc + 30
[1] 0x000000010ea45458 libobjc.A.dylib`class_createInstance + 85
[2] 0x000000010ea4fd55 libobjc.A.dylib`_objc_rootAlloc + 42
[3] 0x000000010de1f19b Foundation`+[NSError errorWithDomain:code:userInfo:] + 37
[4] 0x000000010c1a4a3c CoreData`-[NSPropertyDescription(_NSInternalMethods) _nonPredicateValidateValue:forKey:inObject:error:] + 124
[5] 0x000000010c1a4bc0 CoreData`-[NSRelationshipDescription(_NSInternalMethods) _nonPredicateValidateValue:forKey:inObject:error:] + 80
[6] 0x000000010c1a3b40 CoreData`-[NSManagedObject(_NSInternalMethods) _validateValue:forProperty:andKey:withIndex:error:] + 384
[7] 0x000000010c1a3896 CoreData`-[NSManagedObject(_NSInternalMethods) _validatePropertiesWithError:] + 358
[8] 0x000000010c1a36f7 CoreData`-[NSManagedObject(_NSInternalMethods) _validateForSave:] + 119
[9] 0x000000010c1b3d4c CoreData`-[NSManagedObject validateForInsert:] + 76
[10] 0x000000010c1a2a77 CoreData`-[NSManagedObjectContext(_NSInternalAdditions) _validateObjects:forOperation:error:exhaustive:forSave:] + 1783
[11] 0x000000010c1a2202 CoreData`-[NSManagedObjectContext(_NSInternalAdditions) _validateChangesForSave:] + 146
[12] 0x000000010c1a1f56 CoreData`-[NSManagedObjectContext(_NSInternalChangeProcessing) _prepareForPushChanges:] + 214
[13] 0x000000010c19e972 CoreData`-[NSManagedObjectContext save:] + 562
[14] 0x000000010ce26a9d UIKit`__43-[UIManagedDocument contentsForType:error:]_block_invoke + 30
[15] 0x000000010c1b89a7 CoreData`developerSubmittedBlockToNSManagedObjectContextPerform + 199
[16] 0x000000010c1b885f CoreData`-[NSManagedObjectContext performBlockAndWait:] + 255
[17] 0x000000010ce269f0 UIKit`-[UIManagedDocument contentsForType:error:] + 258
[18] 0x000000010cd9477c UIKit`-[UIDocument saveToURL:forSaveOperation:completionHandler:] + 486
[19] 0x000000010cd962b2 UIKit`__55-[UIDocument _saveUnsavedChangesWithCompletionHandler:]_block_invoke_2 + 156
[20] 0x000000010fd77978 libdispatch.dylib`_dispatch_call_block_and_release + 12
[21] 0x000000010fda10cd libdispatch.dylib`_dispatch_client_callout + 8
[22] 0x000000010fd818a4 libdispatch.dylib`_dispatch_main_queue_callback_4CF + 406
[23] 0x000000010ef9de49 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
[24] 0x000000010ef6337d CoreFoundation`__CFRunLoopRun + 2205
[25] 0x000000010ef62884 CoreFoundation`CFRunLoopRunSpecific + 420
[26] 0x00000001115dfa6f GraphicsServices`GSEventRunModal + 161
[27] 0x000000010c5a1c68 UIKit`UIApplicationMain + 159
[28] 0x000000010bac23bf MyApp`main + 111 at main.m:16:9
[29] 0x000000010fded68d libdyld.dylib`start + 1
[30] 0x0000000110153001 libsystem_pthread.dylib`_thread + 1
Can someone help me diagnose this?