The scenario is you have a federation with a LDAP (e.g. OpenLDAP) and a configured Group Mapper which synchronizes groups between Keycloak DB and OpenLDAP.
The issue is about renaming groups: in Keycloak, when you change a group name and press the "Sync Keycloak to LDAP" button from the group mapper, the old group is not removed in OpenLDAP (so it's still present). However, in Keycloak DB it is removed instead.
Another issue is that group members are removed from the renamed group (both in Keycloak and LDAP), so renamed group will have no members after the operation.