UISearchBar has a strange flash when navigating back?

Copied from: http://stackoverflow.com/questions/31346715/why-does-the-uisearchbar-appear-to-have-a-strange-flash-when-navigating-back

I've got a UISearchBar in my UINavigationItem's titleView associated with a UISearchController. When I navigate back, it appears to flash. Anyone seen this before?

https://www.youtube.com/watch?v=1-0TdqGNROg

    @interface HNTileSearchViewController () <HNTileSearchResultsProtocol, SWRevealViewControllerDelegate, UISearchBarDelegate, HNSetSearchFiltersProtocol, HNKeywordResultsProtocol>
    ...
    @property (nonatomic, strong) UISearchController *searchController;
    @property (nonatomic, strong) UISearchBar * searchBarTop;
    ...
    @end




    @implementation HNTileSearchViewController
    ...
        - (void) customPreSetup {
            HNKeywordResultsTableViewController * searchResultsController = [self.storyboard instantiateViewControllerWithIdentifier:HNKeywordResultsTableViewControllerStoryboardIdentifier];
            searchResultsController.delegate = self;
            _searchController = [[UISearchController alloc] initWithSearchResultsController:searchResultsController];
            _searchController.searchResultsUpdater = searchResultsController;
            _searchController.hidesNavigationBarDuringPresentation = NO;
            _searchController.dimsBackgroundDuringPresentation = NO;
            _searchBarTop = _searchController.searchBar;
            _searchBarTop.delegate = self;
            _searchBarTop.placeholder = NSLocalizedString(@"Search heynay", nil);
            _searchBarTop.showsCancelButton = NO;
            _searchBarTop.showsScopeBar = NO;
            self.navigationItem.titleView = _searchBarTop;
            self.definesPresentationContext = YES;
        }


        - (void) viewDidLoad {
            [super viewDidLoad];
            [self customPreSetup];
            ...
        }
    ....
    @end