Update from 12.0.4 to 15.0.2 deletes ldap users

Hi,

i am trying to update a keycloak instance from version 12.0.4 to 15.0.2.
Upon first access of (realm) users i get a log message similar to this:

2021-10-21 07:40:50,477 INFO  [org.keycloak.storage.ldap.LDAPIdentityStoreRegistry] (default task-1) Creating new LDAP Store for the LDAP storage provider: 'ldap', LDAP Configuration: {pagination=[true], fullSyncPeriod=[-1], connectionPooling=[true], usersDn=[cn=<redacted>,dc=<redacted>,dc=<redacted>,dc=<redacted>], cachePolicy=[DEFAULT], useKerberosForPasswordAuthentication=[false], importEnabled=[true], enabled=[true], usernameLDAPAttribute=[cn], bindDn=[cn=<redacted>,dc=<redacted>,dc=<redacted>,dc=<redacted>], changedSyncPeriod=[-1], lastSync=[1623083435], vendor=[ad], uuidLDAPAttribute=[objectGUID], connectionUrl=[ldap://<redacted>], allowKerberosAuthentication=[false], syncRegistrations=[false], authType=[simple], debug=[false], searchScope=[2], useTruststoreSpi=[ldapsOnly], trustEmail=[false], priority=[0], userObjectClasses=[person, organizationalPerson, user], rdnLDAPAttribute=[cn], editMode=[READ_ONLY], validatePasswordPolicy=[false], batchSizeForSync=[1000]}, binaryAttributes: []

And all my ldap users are gone. Only the local ones are left.

Since it’s a VM (testing-)setup I can reproduce it and provide further info if needed.

Any help much appreciated.