In my case, I get the same error in [UIPageViewController setViewControllers:direction:animated:completion:]. I don't know how to fix this error yet.
Fatal Exception: NSInternalInconsistencyException (Unexpected subviews)
0 CoreFoundation 0x1a0e229d8 __exceptionPreprocess
1 libobjc.A.dylib 0x1b51a5b54 objc_exception_throw
2 CoreFoundation 0x1a0d3150c -[CFPrefsSearchListSource addManagedSourceForIdentifier:user:]
3 Foundation 0x1a202b878 -[NSAssertionHandler handleFailureInMethod:object:file:lineNumber:description:]
4 UIKitCore 0x1a2f3bac4 -[_UIQueuingScrollView _setWrappedViewAtIndex:withView:]
5 UIKitCore 0x1a2f3c04c -[_UIQueuingScrollView _replaceViews:updatingContents:adjustContentInsets:animated:]
6 UIKitCore 0x1a2f3d68c -[_UIQueuingScrollView _enqueueAnimatedScrollInDirection:withView:completion:]
7 UIKitCore 0x1a2f3e1d4 -[_UIQueuingScrollView setView:direction:animated:completion:]
8 UIKitCore 0x1a2f31e14 -[UIPageViewController _setViewControllers:withScrollInDirection:animated:completion:]
9 UIKitCore 0x1a2f31ffc -[UIPageViewController setViewControllers:direction:animated:completion:]