Kea has been working great, but I just updated to 26.1.5 and now Kea assigns a IP address from the pool even though there's a valid reservation for the device.
Restarted Kea, rebooted opnsense and the device still gets a IP address in the network pool.
1) Kea didn't break, works just fine for most of us.
2) Kea is finicky and has had issues in the past with the machine hostnames. It is possible some restriction could have been introduced the latest update
3) You'll need to find out what's so special about the machine hostname that is not getting the reservation anymore and likely open an issue on GitHub opnsense/core
I have a laptop that I occasionally use that has been on a working IP reservation for a long time.
Today I turned it on and was surprised to see it got an IP address in the restricted range(pool).
The MAC showed up in the Kea pool while the reservation also showed the correct MAC. My lease time is set very low,so when the system tried to renew it should have jumped to the reservation, but didn't.
With the IP set manually to the same one as the reservation, the system can now do updates.
Take a look at this post (https://forum.opnsense.org/index.php?msg=263439), it will most probably explain your situation and how to fix it (and knowing the problem will prevent you from creating it again).