UINavigationController jarring push transition

Question

I'm using the latest iOS 7 animation transitions protocols in order to create a fade transition one a push a view controller; a member of the class PSSpaceDetailViewController. However, for all other push transitions, I'd like to use the default push animation that UINavigationController normally provides.

However, having implemented the following code to do exactly that, I'm receiving a strange delayed jarring animation when I push a separate view controller from the aforementioned class. Any ideas why this is happening? I've uploaded a short video showing the animation that I'm trying to describe which will hopefully make it easier to understand the bug: http://d.pr/v/Q754

//PSAnimatngNavigationControllerDelegate.m

+ (instancetype) sharedInstance {
    static PSAnimatingNavigationControllerDelegate *shared;
    static dispatch_once_t onceToken;
    dispatch_once(&onceToken, ^{
        shared = [[PSAnimatingNavigationControllerDelegate alloc] init];
    });
    return shared;
}

- (PSFadeAnimator *) animator {
    if (!_animator) {
        _animator = [[PSFadeAnimator alloc] init];
    }
    return _animator;
}

- (id<UIViewControllerAnimatedTransitioning>)navigationController:(UINavigationController *)navigationController animationControllerForOperation:(UINavigationControllerOperation)operation fromViewController:(UIViewController *)fromVC toViewController:(UIViewController *)toVC
{
    if (operation == UINavigationControllerOperationPush && [toVC isKindOfClass:[PSSpaceDetailViewController class]]) {
        return self.animator;
    }
    return nil;
}

// App Delegate.m

UINavigationController *navigationController = [[UINavigationController alloc] initWithRootViewController:notesViewController];
[navigationController setDelegate:[PSAnimatingNavigationControllerDelegate sharedInstance]];

PSSpaceDetailViewController.m

- (void) tableView:(UITableView *)tableView didSelectRowAtIndexPath:(NSIndexPath *)indexPath {
    PSMatchDetailViewController *matchDetail = [[PSMatchDetailViewController alloc] initWithOriginalSpace:self.space andPotentialLead:self.datasource[indexPath.section][indexPath.row]];
    [self.navigationController pushViewController:matchDetail animated:YES];
}

Answer 1

The view controller you're pushing has an nil background colour, which defaults to clear on iOS 7. Just set it to white or whatever and it'll work.