Xcode swift Segue animation stops working

I have a segue that animates when changing back and forward through views, but after a while it stops animating and instantly changes.

This segue is programatic, I have segues that work perfectly fine when doing it through a storyboard.

func MoreInfo(sender: customButton!) {
    var nextPage: activityViewController = self.storyboard?.instantiateViewControllerWithIdentifier("activityPopOver") as activityViewController

    nextPage.model = sender.model
    nextPage.coordinate = self.coordinate

    self.navigationController?.pushViewController(nextPage, animated: true)

}

that's all the code I'm using to change scenes, my prepare for segue method is empty aswell. I am using a UI view controller aswell