[keycloak-user] Why duplicate records found for user?

I've noticed this behavior with both Keycloak 4.1.0 and Keycloak 5.0.0: when using admin web interface "Users" search duplicate records are found for some users. What could possibly be causing this? I've tried clearing all caches from (Realm Settings > Cache) and I've tried removing imported users (User Federation > ldap storage provider > "Remove Imported" button). Still seeing duplicates for some users. Weird. I've got UUID LDAP attribute set to nsuinqueid with keycloak 4.1.0 and to uid with keycloak 5.0.0 (both pointing to same Red Hat Identity Manager instance). Duplicate users don't seem to be duplicated in LDAP. Maybe group-ldap-mapper is doing something weird? Is this due to Brokered Identities? Or is this just a bug?