Commented Unassigned: Dropdownbutton unexpected IsOpen behaviour [22229]

When you bind IsOpen to a viewmodel property, the DropDownButton control seems to only read the IsOpen value once when the control is created, setting it's initial state. After that, the bound property is never updated or read again as you open and close the popup (or when you modify the viewmodel property). From the description this appears to be incorrect behavior. Has anyone else experienced this?
Comments: ** Comment from web user: curiousKoala **

So after downloading the source for this control, it appears that the "OnKeyDown" handler is not being called when the togglebutton is clicked. WPF is not my strength so this is as far as I've been able to debug this thus far.