Setting UISplitViewController viewControllers Property Causes SIGABRT in iOS 8 - objective-c

Question

In our app we call a method that adds two navigation controllers to a UISplitViewController via the viewControllers property. We do this in multiple places in our app, but this one place is causing a SIGABRT and I cannot figure out why. The UISplitViewController.viewControllers already has two view controllers in the NSArray at this point. The error happens only when the device is in portrait and only on iOS 8.
The error that comes with the SIGABRT is:
*** Terminating app due to uncaught exception 'NSRangeException', reason: '*** -[__NSArrayM objectAtIndex:]: index 11 beyond bounds [0 .. 10]'
The line of code that causes the error is
self.splitViewController.viewControllers = #[mainNav.navigationController, genericNavVC];
It has to be something with the property because it doesn't seem to matter what I try to assign to it (nil, 2 blank UINavigationControllers, etc.). I've also tried using the setViewControllers method but it still errs.
Does anyone know what might be causing this and is there something we could use as a workaround?
-- Extra Info --
NSLog of the exception callStackSymbols:
(
0 CoreFoundation 0x24ce6d7f <redacted> + 150
1 libobjc.A.dylib 0x3285dc77 objc_exception_throw + 38
2 CoreFoundation 0x24bfafb7 <redacted> + 230
3 myApp 0x00212ef7 -[DocsToSign objectAtIndex:] + 62
4 myApp 0x001436d3 -[DocsToSignListViewController tableView:cellForRowAtIndexPath:] + 966
5 UIKit 0x2845126d <redacted> + 476
6 UIKit 0x2845132f <redacted> + 54
7 UIKit 0x28446a51 <redacted> + 2276
8 UIKit 0x2825ec1b <redacted> + 186
9 UIKit 0x28188c1f <redacted> + 514
10 QuartzCore 0x27bb3f65 <redacted> + 136
11 QuartzCore 0x27baf951 <redacted> + 360
12 UIKit 0x2819b367 <redacted> + 138
13 UIKit 0x282358ed <redacted> + 872
14 UIKit 0x2836643d <redacted> + 284
15 UIKit 0x28232803 <redacted> + 78
16 UIKit 0x28480949 <redacted> + 536
17 UIKit 0x286474cd <redacted> + 168
18 UIKit 0x28647283 <redacted> + 138
19 UIKit 0x28474487 <redacted> + 350
20 UIKit 0x28636d13 <redacted> + 170
21 myApp 0x000eb5db -[AppDelegate_iPad ClearDetailView] + 1446
22 myApp 0x001478e9 -[DocsToSignListViewController SignDocsComplete:withResponseData:] + 1564
23 myApp 0x000fbae3 -[WCFHandler requestCompleted] + 846
24 myApp 0x000fc353 -[WCFHandler connectionDidFinishLoading:] + 86
25 CFNetwork 0x24840045 <redacted> + 56
26 CFNetwork 0x2483ffff <redacted> + 182
27 CFNetwork 0x248400f1 <redacted> + 36
28 CFNetwork 0x2475527b <redacted> + 78
29 CFNetwork 0x247f18c5 <redacted> + 60
30 CFNetwork 0x24746189 <redacted> + 60
31 CoreFoundation 0x24bf83f1 CFArrayApplyFunction + 36
32 CFNetwork 0x24746043 <redacted> + 182
33 CFNetwork 0x24745f09 <redacted> + 216
34 CFNetwork 0x24745da5 <redacted> + 48
35 CoreFoundation 0x24cad5e7 <redacted> + 14
36 CoreFoundation 0x24cac9fb <redacted> + 222
37 CoreFoundation 0x24cab079 <redacted> + 768
38 CoreFoundation 0x24bf8981 CFRunLoopRunSpecific + 476
39 CoreFoundation 0x24bf8793 CFRunLoopRunInMode + 106
40 GraphicsServices 0x2bfa8051 GSEventRunModal + 136
41 UIKit 0x281ea981 UIApplicationMain + 1440
42 myApp 0x000e8a09 main + 48
43 libdyld.dylib 0x32df9aaf <redacted> + 2
)
And this is from calling thread backtrace at exception time:
* thread #1: tid = 0x2259, 0x000eb71c myApp`-[AppDelegate_iPad ClearDetailView](self=0x15571b80, _cmd=0x002b2ecd) + 1768 at AppDelegate_iPad.m:332, queue = 'com.apple.main-thread', stop reason = step over
* frame #0: 0x000eb71c myApp`-[AppDelegate_iPad ClearDetailView](self=0x15571b80, _cmd=0x002b2ecd) + 1768 at AppDelegate_iPad.m:332
frame #1: 0x001478e8 myApp`-[DocsToSignListViewController SignDocsComplete:withResponseData:](self=0x155b7820, _cmd=0x002b968f, handler=0x15511f10, responseData=0x1558ef90) + 1564 at DocsToSignListViewController.m:690
frame #2: 0x000fbae2 myApp`-[WCFHandler requestCompleted](self=0x1550b040, _cmd=0x2bf7076d) + 846 at WCFHandler.m:161
frame #3: 0x000fc352 myApp`-[WCFHandler connectionDidFinishLoading:](self=0x1550b040, _cmd=0x2898e975, connection=0x15567af0) + 86 at WCFHandler.m:243
frame #4: 0x24840044 CFNetwork`__65-[NSURLConnectionInternal _withConnectionAndDelegate:onlyActive:]_block_invoke + 56
frame #5: 0x2483fffe CFNetwork`-[NSURLConnectionInternal _withConnectionAndDelegate:onlyActive:] + 182
frame #6: 0x248400f0 CFNetwork`-[NSURLConnectionInternal _withActiveConnectionAndDelegate:] + 36
frame #7: 0x2475527a CFNetwork`___ZN27URLConnectionClient_Classic26_delegate_didFinishLoadingEU13block_pointerFvvE_block_invoke + 78
frame #8: 0x247f18c4 CFNetwork`___ZN27URLConnectionClient_Classic18_withDelegateAsyncEPKcU13block_pointerFvP16_CFURLConnectionPK33CFURLConnectionClientCurrent_VMaxE_block_invoke_2 + 60
frame #9: 0x24746188 CFNetwork`RunloopBlockContext::_invoke_block(void const*, void*) + 60
frame #10: 0x24bf83f0 CoreFoundation`CFArrayApplyFunction + 36
frame #11: 0x24746042 CFNetwork`RunloopBlockContext::perform() + 182
frame #12: 0x24745f08 CFNetwork`MultiplexerSource::perform() + 216
frame #13: 0x24745da4 CFNetwork`MultiplexerSource::_perform(void*) + 48
frame #14: 0x24cad5e6 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_SOURCE0_PERFORM_FUNCTION__ + 14
frame #15: 0x24cac9fa CoreFoundation`__CFRunLoopDoSources0 + 222
frame #16: 0x24cab078 CoreFoundation`__CFRunLoopRun + 768
frame #17: 0x24bf8980 CoreFoundation`CFRunLoopRunSpecific + 476
frame #18: 0x24bf8792 CoreFoundation`CFRunLoopRunInMode + 106
frame #19: 0x2bfa8050 GraphicsServices`GSEventRunModal + 136
frame #20: 0x281ea980 UIKit`UIApplicationMain + 1440
frame #21: 0x000e8a08 myApp`main(argc=1, argv=0x0054cafc) + 48 at main.m:14