Issues with 24.7 upgrade, and solution. Upgrade bug?

[dwasifar]

After upgrading to 24.7, half my network didn't work. So the last few days have been back and forth between my backup opnsense box and the production box, trying different things as time allowed.

I tried a clean install of 24.7 and applied backup config. No help. Then I remembered the upgrade notes mentioned some function had been removed from old DCHP for backward compatibility with Kea. So I switched to Kea on my 24.7 install. No help there. I migrated the same Kea setup back to 24.1.10. That worked.

Some more investigating and I determined all the problem devices were trying to connect through a VLAN interface I have set up to keep IOT devices isolated. I tried connecting to that network with my phone and it failed, telling me it couldn't get an IP. So I still thought it was a DCHP issue, but I decided to check the VLAN setup anyway, and in the Interfaces summary page, the parent interface was unpopulated. I opened the edit popup, and the parent WAS populated there. Saved it, and the summary page then showed that field populated, and everything started working normally.

So maybe this is an upgrade bug. The upgrade killed my VLAN but resaving its configuration fixed it.