title: Unable to see animation for .transitionFlipFromRight for first 3 view controllers in array
body: <p>I have an app with a Tinder-like interface where a user can flip through car</p>
  
  <p>In my <code>ViewController.swift</code>, I have</p>
  
  <p><code>private var currentCardsOnScreen: [CardViewController] = []</code></p>
  
  <p>This array gets populated as I put <code>CardViewController</code>s in the stack:</p>
  
  <pre><code>if !currentCardsOnScreen.map({ $0.id }).contains(vc.id) {
      self.currentCardsOnScreen.append(vc)
  }
  </code></pre>
  
  <p>And items get removed after the swipe happens:</p>
  
  <pre><code>if let index = currentCardsOnScreen.index(of: currentCard), 
      currentCardsOnScreen.map({ $0.id }).contains(currentCard.id) {
           currentCardsOnScreen.remove(at: index)
   }
  </code></pre>
  
  <p>When the user selects a card, I run this:</p>
  
  <pre><code>guard let currentCard = currentCard(index: index) else { return }
  
  currentCard.flipCard()
  </code></pre>
  
  <p>Which calls this method:</p>
  
  <pre><code>func flipCard() {
      guard
          let frontOfCard = frontOfCard,
          let backOfCard = backOfCard
      else { return }
  
      UIView.animate(withDuration: 0.32, delay: 0, options: .transitionFlipFromRight, animations: {
          if self.frontIsShowing {
              self.view.transform = CGAffineTransform(scaleX: 1, y: 1)
  
              frontOfCard.alpha = 0
              backOfCard.view.alpha = 1
          } else {
              self.view.transform = CGAffineTransform(scaleX: -1, y: 1)
              frontOfCard.transform = CGAffineTransform(scaleX: -1, y: 1)
  
              frontOfCard.alpha = 1
              backOfCard.view.alpha = 0
          }
  
          self.frontIsShowing = !self.frontIsShowing
      }, completion: nil)
  </code></pre>
  
  <p>The number of cards in the stack is always 3. For the first 3 cards, tapping the card will change the value of <code>frontIsShowing</code> but won't show the card flip. If I swipe away the first 3, any card after that will behave as intended. The animation will show and all will be good.</p>
  
  <p>Any ideas what could be going on here?</p>
  
  <p><strong>Edit:</strong> Also, not sure if related, but on card 4 when it makes the first flip animation, I see the alphas transition via a fade in/fade out but not a card flip. On the second click is when I see that flip animation. Again, not sure if related but thought I'd mention.</p>