WPF PDFViewer form fields don't update after initially setting them Declined - Won't do

In the WPF PDFViewer control, after loading a document and setting the form fields initially (in code), changing the values of the fields (from code) does not update the displayed PDF's form fields.  However, after changing the field's values, if you resize the form, the PDF appears to refresh and the new values are then displayed.  I figured that I may need to do some kind of refresh manually but cannot find any method that would do this (and I would think this should not be necessary).

I have included a sample project.  You can run it, hit "Load" and load a PDF with form fields.  You should see that the text fields in the PDF are loaded with some default data. Next hit the "Update Fields" button. This should update all the text fields with the current time, however you will not see the fields update.  If you then resize the form, the fields will be refreshed and you should see the time in the text fields.