As part of learning UIPresentationController (and its associated custom view controller presentation objects) I figured I'd recreate Apple's iOS 13 default modal presentation style. It worked well-enough on iOS 12 and 13, but on iOS 14 I get this weirdness (also note how when dismissing the presentingVC snaps to be proper position it's supposed to have). Did something change? The relevant code for the applied transform is:
let ratio = (UIScreen.main.bounds.width - 32) / UIScreen.main.bounds.width
let height = frameOfPresentedViewInContainerView.height
let newHeight = height * ratio
let translation = (height - newHeight) / 2
return CGAffineTransform.init(scaleX: ratio, y: ratio).concatenating(.init(translationX: 0, y: -translation - 10))
It's worth noting that presenting the first VC (which the video starts with it already presented) works just fine, as does presenting a new VC.
Edit: Resolved! Thanks to this comment, turns out it's a bug with transforms.