When adding newer domain Controllers to a MS network, we might be using the old FRS and we have to upgrade to DFRS https://www.rebeladmin.com/2015/04/step-by-step-guide-for-upgrading-sysvol-replication-to-dfsr-distributed-file-system-replication/ https://techcommunity.microsoft.com/t5/storage-at-microsoft/streamlined-migration-of-frs-to-dfsr-sysvol/ba-p/425405