ProgressBar not updating in ListView on UWP

We have a ListView with a custom ViewCell containing a ProgressBar with a binding on the progress property.
The value in the view model is being changed and the property change notification is firing OK, but the progress bar is not updated on UWP.
Note: Works fine on Android, iOS.

For testing, I have created a custom renderer for ProgressBar on UWP to intercept the OnElementChanged and OnElementPropertyChanged methods.
Source code for the stock renderer is located here

• Native control is being initialised correctly.
• OnElementPropertyChanged is being fired and I can see the value of Element.Progress being changed.
• ProgressBarOnValueChanged event is being fired which calls InvalidateMeasure on the element.

So...everything under the hood looks OK, but the UI does not update.
Anybody else seeing this?

Tested with Xamarin.Forms 2.3.3.193, Windows 10 Anniversary Update.