LDAP Authentik not working with every user

[Snwy]

Hello everyone,

I'm running an instance of authentik with an LDAP Outpost managing the requests over the Jellyfin LDAP Authentication plugin.
I entered all the values and all the tests can query my instance successfully aswell as return the correct user count for my user and admin filters.

Now when I try to login with two different accounts called Admin & user the results differentiate.
- The admin account processes the login
- The user account returns a "failed username or password"

Logs:

Code:

[15:16:12] [WRN] [29] Jellyfin.Plugin.LDAP_Auth.LdapAuthenticationProviderPlugin: User Manager could not find an user with such ldapUid, this may not be fatal
System.NullReferenceException: Object reference not set to an instance of an object.
  at Jellyfin.Plugin.LDAP_Auth.LdapAuthenticationProviderPlugin.Authenticate(String username, String password)
[16:14:12] [WRN] [29] Jellyfin.Plugin.LDAP_Auth.LdapAuthenticationProviderPlugin: User Manager could not find an user with such ldapUsername, this may not be fatal
System.NullReferenceException: Object reference not set to an instance of an object.
  at Jellyfin.Plugin.LDAP_Auth.LdapAuthenticationProviderPlugin.Authenticate(String username, String password)
[16:14:14] [ERR] [29] Jellyfin.Plugin.LDAP_Auth.LdapAuthenticationProviderPlugin: Failed to Connect or Bind to server as user cn=user,ou=users,dc=replaced,dc=de
LdapException: Invalid Credentials (49) Invalid Credentials
LdapException: Matched DN:
[16:14:14] [INF] [29] Jellyfin.Server.Implementations.Users.UserManager: Authentication request for user has been denied (IP: 78.255.255.255).
[16:14:14] [ERR] [29] Jellyfin.Api.Middleware.ExceptionMiddleware: Error processing request: Invalid username or password entered. URL POST /Users/authenticatebyname.

So my question is now: Are there any additional ways that I can try to troubleshoot my error and why the heck the login only works with this account :D