Make sure you have at least two users with workflow access to an article
Log in as the first user
Open the article
Set the Assignee to the second user and save the article
--> When the user is bound to a relation, the facet navigation shows the assignee. So the assignee seems to be changed. That's OK.
Open the article again
The current user is selected in the Assignee select box. --> That's not OK.
Maybe this has something to do with selecting the current user as default assignee for a new article. This should not be done with existing articles.