bp_displayed_user_fullname() not working anymore

Some time ago I have build an intranet for a company using Buddypress. Everything had been fine but recently I have got this problem:
In the member directory overview it is working fine, I see the users full names below there pics but on the single member pages it shows the nickname (@a-gordijnairborne-nl) in stead of the full name.
I have copied several buddypress files to my theme directory. In member-header.php I use the following code: "><?php bp_displayed_user_fullname(); ?>

As said before, this used to work but now it is showing some kind of nickname. I checked as much as possible: Extended profiles is active and so on but it won't work.
It looks like a recent update caused this.

I cannot give you access before asking the client because it's a intranet for employees but maybe you recognize the problem en know what has changed and can you help me whitout login.

I really would like to hear from you,
Thanks in advance,