Another Gitlab add member 500 error

URL of experiment:
(Sign in · GitLab)

Description of the problem: I think I have a similar problem to @Steven_Elmlinger (Gitlab add member 500 error)

In the Gitlab Interface of my experiment, I am trying to add members by going to Settings>Members, but then I get a 500 error from the website. I think this is happening because I previously invited a member who was not already a Pavlovia/Gitlab account holder.

Is it possible for a website admin to fix this issue, or let me know what I should do?