Comment 4 for bug 1896292

Could maas analyse modification to dynamic ranges as they happen and do the cleanup then ? Even if the IP is stll in use, ADMIN should be able to remove the range and cause the observed IPs cleanup.

Another idea, leases are not just cleared. Dhcp config is altered. Can hook be configured on the dhcpd to also invoke dhcp helper for all ips which are by new configuration out of range ?

Just throwing some ideas. The suggested ones are also fine.
Most of all, I would also inquire about static/dynamic IPS hiding behind a bond or bridge. Can you please spend some time checking if those get cleared cause if I remember, we found one instance hanging on a secondary physical interface which is part of a bond.

Regards,
Igor