1) Removing member form project works fine.
2) However, adding a project member fails and causes a blank page.
3) Browser dev tools show a 500 error for a second. (response headers attached)
Note 01): my Tuleap installation is over a year old. Hence, I'm trying to add users that are also "unix" users. This may refer to this tracker's request #10782
"Disable usage of unix users and groups" in this tracker.
Note 02): A week ago even the search field for adding users did not work. Only after recent updates around previous Monday, the search field resumed to work. Now it finds users I want to add. The "add member" button still causes blank screen with 500 error.