Why is the iOS 11: self.performSegue() not working?

Question

I started the migration to Xcode 9 & iOS 11 build today.

In my storybased app, the following code:

self.performSegue(withIdentifier: Const.UI.Segue.showIntro, sender: self)

runs fine in all previous iOS (just verified with iOS 10.3, 10.0, 9.0) but does not run in iOS 11.

Additional code:

private func handleSuccessfulLogin() {
    self.log.info("Logged In")
    DispatchQueue.main.async(){
        self.performSegue(withIdentifier: Const.UI.Segue.showIntro, sender: self)
    }
}

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    print("starting segue " + segue.identifier!)
}

override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
    print("should perform segue")
    return true
}

printout (iOS 11):

> Logged In
> starting segue showIntroSegue

Expected result: new controller pushed

Actual result iOS 11: nothing at all happens

Any ideas what the reason might be?

The function handleSuccessfulLogin() is called after a successful login with AWSCognito / AWSFacebookSignInProvider, a facebook login. On iOS there is a new popup continue with facebook which I suspect to be the reason, but I got no way to verify it.. On the 2nd call this popup does not appear (as facebook already is authorized), and then the segue triggers correctly.

Note, I also tried this snippet, same result.

OperationQueue.main.addOperation {
        [weak self] in
        self?.performSegue(withIdentifier: Const.UI.Segue.showIntro, sender: self)
    }

Answer 1

I found the solution to be at a completely different place (as so often). The reason was that I had a logic in place in applicationDidBecomeActive that was replacing the current storyboard (bad approach!) - the additional popup from the FB Kit led to a recreation of my container view controller. Thus i had self.navigationController == nil during the call to perform the segue.