NavigationController.PopViewController not popping top view controller

Question

Hello,
I have a Xamarin.iOS project where at some point I call NavigationController.PopViewController(true);
However, the view which I'm trying to pop doesn't go away. It's as if PopViewController isn't doing anything
The NavigationController isn't null, and it has two elements on its stack. The presenting view controller is a UIAlertController that isn't on the stack.
The issue doesn't always happen, but it's pretty easily reproduceable

The issue exists even with the most recent version of Xamarin.Forms.

I notice that (unsurprisingly) in the cases that the view is dismissed, the ViewWillDisappear method is invoked. But it isn't called when the view isn't dismissed

Any ideas what might be going wrong? Any chance I'm doing something wrong?