Have you tried tapping the breakpoints to enable/disable them. The only time I have had a breakpoint not work is when it is disabled, especially since your print method is firing. Another thing to try is "Clean Build Folder" under the "Product" menu, even though you did mention that you cleared the Derived Data. Also don't forget to call super.traitCollectionDidChange(previousTraitCollection) after your override func. Even though the default method for traitCollectionDidChange is empty, if you have views higher up in your hierarchy, they need a chance to respond to the method as well. Curious what you find out and what suggestions others may have.

Does the UIView that you pass to the animateButtonView function contain the self.addToFavoritesButton? If that is the case, you should get the pointer to it from the UIView you pass instead of the local variable. This would cause a cell reuse problem if that view is in your collection view.