Despite some domains were disabled, its DNS zone are propagated to NS.
Software issue #OA-11506 The DNS zones of disabled domain are propagating to nameservers when API pem.syncNameServers is called for that domain.
Issue is fixed in OA 8.4.
To work around the issue you can enable/disable domain through PCP.
To go through all disabled domain and disable them again, download the script to management node and run. The script searched for all disabled domains and calls pem.disableDomain for each one.