Outlook Issue - Dialog box

Hi guys, I have a user experiencing an old known bug in Outlook. Error message below: 

"The properties of the message have been changed" prompt when forwarding/replying in Outlook

I have updated outlook, recreated the profile, ran an online repair, .olded the reg value and even checked the mail settings to see if there was a cause there. None of this has fixed the issue unfortunately. 

Any ideas?