Our DHCP was set to lease addresses for 1 day, for reasons which were never explained to me.
I'm wondering if I remove all records which don't have the service account present, will these then be regenerated correctly, and updated properly going forward? You can try deleting some of the outdated records, and then either let DHCP refresh the records or do an ipconfig /registerdns from the client. You still should be looking at why scavenging is not running in your environment.
All records with a timestamp of today (specifically the two machines we just rebuilt) don't have the service account in the permissions - they do have their own computer account, and the owner is SYSTEM.
Discard A and PTR records when lease is deleted Dynamically update for DHCP clients that do not request updates Our domain's zone is configured as an AD-Integrated zone with replication to all DNS servers in the forest.
As far as my understanding goes (which is clearly not far enough), DHCP should update DNS as soon as it itself updates.
However in your aging settings, the record is able to be marked for scavenging after 8 hours (no-refresh refresh intervals). Under Server Manager, have you tried running the Best Practices Analyzer against DNS and DHCP, to see if that gleams any info?