Case owner displayed as "First Last"

Hi, for one user in our CRM 2016 Online, who is the owner of some cases, the Full Name is being displayed exactly as "First Last" next to the Owner Label. I have a e-mail template which uses the Owner field and the name of this user is displayed the same way when the template is used in an e-mail. The same problem occurs when a view displays the owner of cases and for this particular user, the Full Name is displayed with the same error.

I am totally sure the Full Name is correctly entered in the user´s properties.

Any idea would be much appreciated.

Xavier Villafuerte