One tabBarItem draws two images occasionally - ios

Question

I can't figure out how did this happened.But there is something i have done may cause it.
1,I have swizzled viewDidLoad & viewDidAppear in UIViewController.
2,The AppDelegate's window's rootViewController is a mainViewController(UIViewController).
And I add customNavigationController.view to mainViewController.view.
CustomNavigationController's rootViewController is a UITabbarController.
3,Thread problem?
4,This happened randomly when i tap and pan on the screen frequently.
Here is My code :
In my Custom UITabBarController
- (void)loadViewControllers {
HomeViewController *homeVC = [[HomeViewController alloc] init];
[homeVC.tabBarItem setImage:[UIImage imageNamed:#"Home"]];
[homeVC.tabBarItem setTitle:homeTab];
ProductsViewController *productsVC = [[ProductsViewController alloc] init];
[productsVC.tabBarItem setImage:[UIImage imageNamed:#"Products"]];
[productsVC.tabBarItem setTitle:productsTab];
DiscoverViewController *discoverVC = [[DiscoverViewController alloc] init];
[discoverVC.tabBarItem setImage:[UIImage imageNamed:#"Discover"]];
[discoverVC.tabBarItem setTitle:discoverTab];
AssetsMainViewController *assetsVC = [[AssetsMainViewController alloc] init];
[assetsVC.tabBarItem setImage:[UIImage imageNamed:#"Assets"]];
[assetsVC.tabBarItem setTitle:assetsTab];
NewsViewController *newsVC = [[NewsViewController alloc] init];
[newsVC.tabBarItem setImage:[UIImage imageNamed:#"News"]];
[newsVC.tabBarItem setTitle:newsTab];
[self setViewControllers:#[homeVC,productsVC, discoverVC, assetsVC, newsVC]];
}
In mainViewController:
- (void)loadViewController {
TJSNavigationController *rootNavi = [[TJSNavigationController alloc] initWithRootViewController:[TJSTabBarController sharedSingleton]];
[rootNavi.view setFrame:CGRectMake(0, 0, tMeasure_Width_Sreen, tMeasure_Height_Screen)];
[self.view addSubview:rootNavi.view];
[[TJSTabBarController sharedSingleton] loadViewControllers];
[[TJSTabBarController sharedSingleton] setDelegate:self];
}