Usernames changed after 2nd login

Description

Our rocket.chat server is configured to authenticate with our AD. So when a user logs in for the 1st time, his user is created in rocket.chat.
But when the user logs in for the 2nd time, his username in rocket.chat is changed to something like 0e6b4ad34fc42a45b9a7eb79df464b91. Does anyone have an idea where this behavior comes from?
Also, when the user is deleted, and recreated upon a new login. And then gets again the username change, it changes to the exact same string again. Of course this string is different for every username.

Any help is appreciated!

Server Setup Information

  • Version of Rocket.Chat Server: 6.1.4
  • Operating System: CentOS Stream 8
  • Deployment Method: tar/manual install
  • Number of Running Instances: 1
  • DB Replicaset Oplog:
  • NodeJS Version: 14.21.3
  • MongoDB Version: 5.0.15
  • Proxy: nginx
  • Firewalls involved:

Any additional Information