Buttons not clickable when inside a StackView inside a StackView - cocoa-touch

Question

I have a UIView Subclass which presents three buttons arranged with two above one. I use a StackView to arrange the top two buttons, and the bottom arranged view is just a single button. The problem is that the button added as an arrangedSubview to the root StackView receives clicks, while the buttons inside of the StackView in the StackView do not.
(note: dependencies should not be affecting anything. DynamicButton is just a cocoapod UIButton subclass. InsetView is my own UIView subclass that embeds the buttons in a view with constraints. And pinTo is just a UIView extension that adds pinning constraints to the view. These things shouldn't be the bug given that the bottom button receives clicks and is under the same conditions as the top two buttons.)
class PathContentView: UIView {
let previousButton: DynamicButton = {
let r = DynamicButton(style: .caretLeft)
r.lineWidth = 3
r.strokeColor = .white
r.highlightStokeColor = .gray
return r
}()
let nextButton: DynamicButton = {
let r = DynamicButton(style: .caretRight)
r.lineWidth = 3
r.strokeColor = .white
r.highlightStokeColor = .gray
return r
}()
let deleteButton: DynamicButton = {
let r = DynamicButton(style: .close)
r.lineWidth = 3
r.strokeColor = .white
r.highlightStokeColor = .gray
return r
}()
init() {
super.init(frame: .zero)
setup()
}
override init(frame: CGRect) {
super.init(frame: frame)
setup()
}
private func setup() {
// button components
let deleteButtonHolder = InsetView(width: 25, height: 25, view: deleteButton)
let previousButtonHolder = InsetView(width: 25, height: 25, view: previousButton)
let nextButtonHolder = InsetView(width: 25, height: 25, view: nextButton)
let rootStackView = UIStackView()
let topSectionStackView = UIStackView()
topSectionStackView.distribution = .fillEqually
topSectionStackView.alignment = .center
topSectionStackView.spacing = 20
topSectionStackView.axis = .horizontal
rootStackView.axis = .vertical
rootStackView.distribution = .fillEqually
rootStackView.alignment = .fill
rootStackView.isLayoutMarginsRelativeArrangement = true
rootStackView.layoutMargins = UIEdgeInsets(top: 5, left: 5, bottom: 5, right: 5)
addSubview(rootStackView)
topSectionStackView.addArrangedSubview(previousButtonHolder)
topSectionStackView.addArrangedSubview(nextButtonHolder)
rootStackView.addArrangedSubview(deleteButtonHolder)
rootStackView.addArrangedSubview(topSectionStackView)
rootStackView.pinTo(superView: self)
rootStackView.isUserInteractionEnabled = true
topSectionStackView.isUserInteractionEnabled = true
}
required init?(coder aDecoder: NSCoder) {
fatalError()
}
func tapped() {
print("tapped")
}
}