"Portrait-only" app presenting a landscape-only modal. What is the recommended way to do this and have a seamless modal dismissal?

override var supportedInterfaceOrientations: UIInterfaceOrientationMask {
    return [.landscapeRight, .landscapeLeft]
}

My modal view controller overrides this property, as its a complex custom video player that needs to be restricted to landscape. However, when it's dismissed, there is a jarring bug in the transition where the presenting VC is portrait in the device's landscape state for a second while half of the screen is black. It returns to normal (portrait) after a second, but I would like to avoid this transition bug.

What might I be missing as to the root cause, or recommended way to have a portrait app (set in project navigator) present a landscape-only view controller?

"Portrait-only" app presenting a landscape-only modal. What is the recommended way to do this and have a seamless modal dismissal?
 
 
Q