SSO login failed

Hi, got in Syslog this error occuring in case of SSO-Login at Website:

Aug 14 14:26:47 mmnucs simplesamlphp[9127]: 7 [ddd7dcfd51] Library - LDAP bind(): Extended Error: invalid DN
Aug 14 14:26:47 mmnucs simplesamlphp[9127]: 3 [ddd7dcfd51] Library - LDAP bind(): Bind failed with DN ‘administrator’; cause: ‘Invalid DN syntax’ (0x22); additional: ‘invalid DN’

and login fails.
LDAP in general is working fine, authenticating via Kerberos at AD works. Initializing SSO context is working too:

Aug 14 15:15:49 mmnucs simplesamlphp[19395]: 7 [ddd7dcfd51] Has 1 candidate keys for validation.
Aug 14 15:15:49 mmnucs simplesamlphp[19395]: 7 [ddd7dcfd51] Validation with key #0 succeeded.
Aug 14 15:15:49 mmnucs simplesamlphp[19395]: 6 [ddd7dcfd51] SAML2.0 - IdP.SSOService: incoming authentication request: ‘https://mmnucs.mmn-buero.de/univention/saml/metadata
Aug 14 15:15:49 mmnucs simplesamlphp[19395]: 7 [ddd7dcfd51] loading key simpleSAMLphp.session.1cce60d2c74d980637866b9abcacaf58 from memcache
Aug 14 15:15:49 mmnucs simplesamlphp[19395]: 7 [ddd7dcfd51] saving key simpleSAMLphp.session.1cce60d2d74d980617866b9abcacaf58 to memcache
Aug 14 15:15:49 mmnucs simplesamlphp[19396]: 7 [ddd7dcfd51] backend - fallback: univention-ldap
Aug 14 15:15:49 mmnucs simplesamlphp[19396]: 7 [ddd7dcfd51] Saved state: ‘_916a36c09da6bc265d6afea244602676068ce67927:https://mmnucs.mmn-buero.de/simplesamlphp/saml2/idp/SSOService.php?spentityid=https.mmn-buero.de&cookieTime=1692018949&RelayState=
Aug 14 15:15:49 mmnucs simplesamlphp[19396]: 7 [ddd7dcfd51] Loading state: ‘_916a36c09da6bc265dbafea224602676068ce67927:https://mmnucs.mmn-buero.de/simplesamlphp/saml2/idp/SSOService.php?spentityid=https.mmn-buero.de&cookieTime=1692018949&RelayState=
Aug 14 15:15:49 mmnucs simplesamlphp[19396]: 7 [ddd7dcfd51] loading key simpleSAMLphp.session.1cce60d2c74d980617866b9abcacaf58 from memcache
Aug 14 15:15:49 mmnucs simplesamlphp[19396]: 7 [ddd7dcfd51] saving key simpleSAMLphp.session.1cce60d2c74d980617866b9abcacaf58 to memcache
Aug 14 15:15:49 mmnucs simplesamlphp[19397]: 7 [ddd7dcfd51] Localization: using old system
Aug 14 15:15:49 mmnucs simplesamlphp[19397]: 7 [ddd7dcfd51] Template: Reading [/usr/share/simplesamlphp/dictionaries/login]
Aug 14 15:15:50 mmnucs simplesamlphp[19397]: 7 [ddd7dcfd51] Template: Reading [/usr/share/simplesamlphp/modules/univentiontheme/dictionaries/login]
Aug 14 15:15:50 mmnucs simplesamlphp[19397]: 7 [ddd7dcfd51] Loading state: ‘_916a36c09da6bc265dbafea224602676068ce67927:https://mmnucs.mmn-buero.de/simplesamlphp/saml2/idp/SSOService.php?spentityid=https.mmn-buero.de&cookieTime=1692018949&RelayState=
Aug 14 15:15:50 mmnucs simplesamlphp[19397]: 7 [ddd7dcfd51] loading key simpleSAMLphp.session.1cce60d2c74d980617466b9abcacaf58 from memcache

Please help me to find the problem.
THX

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