it seems like I updated Xcode and suddenly my app's UI broke.
The UIViewController is embedded in a Navigation bar, and the parent viewcontroller is visible behind it.

it seems like I updated Xcode and suddenly my app's UI broke.
The UIViewController is embedded in a Navigation bar, and the parent viewcontroller is visible behind it.

You're presenting this ViewController modally. By default UIViewController.modalPresentationStyle is .automatic, and it's .pageSheet in most cases on iOS 13.
You should specify modal presentation style, when presenting that ViewController. It's should look like
let vc = SomeVC()
vc.modalPresentationStyle = .overFullScreen
present(vc, animated: true)
In storyboard, you should tap on Segue and change it's Presentation
For details, you can visit that medium blog.