Need help with retrieving a user property from an Outlook mail item.

We add some custom properties to Outlook emails we create in our application. In some rare cases we are not able to read the user properties we have added to a an Outlook mail item. I can see that the properties exist, using OutlookSpy, or showing the property value in a column in Outlook. However when using "[login to view URL]" nothing is returned. (See attached example code) I have an .msg file where this problem exists, and will provide this file. When putting this file in the inbox, and running the example code, the user properties are not found, even dough they are shown in OutlookSpy.