UIAlertController sometimes prevents UIRefreshControl to hide

I'm using UIRefreshControl on my tableview to update items. And the end, I show a UIAlertController to inform the user that the update was complete, and how many items were updated. Pretty straightforward, and it works fine for one thing. If I pull to refresh several times in a row, sometimes the refresh control is not dismissed, even after dismissing the alert. I need to swipe up the table to make it go away.

This is the code I use, all UI stuff is nicely done on the main thread:

    if(refreshControl.refreshing) {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            [self refreshItems];

            dispatch_async(dispatch_get_main_queue(), ^{
                [refreshControl endRefreshing];
                [self.tableView reload];
                [self showUpdateInfo];                     
            });
        });
    }

Any idea what could cause this?

EDIT: This is how I create the refresh control in code (in viewDidLoad):

UIRefreshControl *refreshControl = [[UIRefreshControl alloc] init];
refreshControl.attributedTitle   = [[NSAttributedString alloc] initWithString: @"Checking for updates…"];
[refreshControl addTarget: self
                   action: @selector(refreshOutdatedItems)
         forControlEvents: UIControlEventValueChanged];

self.refreshControl = refreshControl;

I believe it really has to do with the tableView not scrolling back up before the UIAlertController is presented. I tried to set the delay for showUpdateInfo method and that seems to worked. I guess when the user only pulls once it will take half a second to show the UIAlertController check if that helps. Here is my code

- (void)refreshOutdatedItems
{
    NSLog(@"refresh");

    if (self.refreshControl.refreshing) {
        dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
            for (double i = 0 ; i < 100000000; i++){

            };

            dispatch_async(dispatch_get_main_queue(), ^{

                [self.refreshControl endRefreshing];
                [self performSelector:@selector(showUpdateInfo) withObject:nil afterDelay:0.5];

            });
        });
    }
}

Let me know if helps.