Using keycloak as sso provider always uses the same user to login

This is my configuration:

- OAUTH_ENABLED=true
- OAUTH_ALLOW_SSO=Keycloak
- OAUTH_BLOCK_AUTO_CREATED_USERS=false
- OAUTH_AUTO_LINK_LDAP_USER=false
- OAUTH_AUTO_LINK_SAML_USER=true

- OAUTH2_GENERIC_NAME=Keycloak
- OAUTH2_GENERIC_APP_ID=git
- OAUTH2_GENERIC_APP_SECRET=secret
- OAUTH2_GENERIC_CLIENT_SITE=https://url
- OAUTH2_GENERIC_CLIENT_USER_INFO_URL=https://url/realms/realm/protocol/openid-connect/userinfo
- OAUTH2_GENERIC_CLIENT_AUTHORIZE_URL=https://url/realms/realm/protocol/openid-connect/auth
- OAUTH2_GENERIC_CLIENT_TOKEN_URL=https://url/realms/realm/protocol/openid-connect/token
- OAUTH2_GENERIC_CLIENT_END_SESSION_ENDPOINT=https://url/realms/realm/protocol/openid-connect/logout

- OAUTH2_GENERIC_USER_UID=preferred_username
- OAUTH2_GENERIC_USER_NAME=name
- OAUTH2_GENERIC_USER_EMAIL=email

Everytime a keycloak user clicks the Keycloak button to login, he gets logged in with my user account.

For example:

John Doe => logs in via keycloak => gets Niklas Hanft as Gitlab user.

The user creation with sso should is enabled, but skipped when John Doe tries to login (he has no account yet)

Every other application I am using with keycloak does not behave this way, so I assume its an issue with the gitlab config.

Start by reproducing the login flow with the listed OAUTH and OAUTH2_GENERIC environment variables, comparing the user information returned for different Keycloak accounts. Trace the generic OAuth/SSO configuration and verify that each Keycloak user maps to a distinct GitLab account, with account creation enabled for users who have no existing account.