Accessory Already in Another Home! Adding any new device fails.

I tried to add a new accessory into my Apple Home environment. It failed. I tried again and now I get the following error when trying to add the same accessory or another new one: Accessory Already in Another Home. I have reset these accessory's to factory (they were brand new). I have rebooted all home hubs, my phone, power cycled the router, and even just today upgraded all to 26.3. No luck.

What else can I try, other than the brute force of deleting and rebuilding my home from scratch. This is not something I am keen to do, if at all possible.

Any ideas how to fix the issue -- seems like the HomeKit DB is corrupted somehow.

Thanks.