Swift Unbalanced calls to begin/end appearance transitions for

This issue occurs if you trying to push new view controller while previous transaction (animation) in progress. So please check your code flow and make the appropriate changes. Check your dismiss and present view animations. You can use property setAnimation to 'YES/NO'resolve this

Set animated:NO, may be solve your problem

To me this weird issue was occurring due to following line after implementation of UISplitViewController

func application(application: UIApplication, didFinishLaunchingWithOptions launchOptions: [NSObject: AnyObject]?) -> Bool {
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    // splitViewController.preferredDisplayMode = .PrimaryOverlay
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    }

By commenting this line in didFinishLaunchingWithOptions issue was resolved.