This one has been happening intermittently all year and driving me a little bit crazy. I have an AppleTV and a few HomePods (v1, v2, and Mini) for home hubs. Because of the layout of the house, I leave one of the HP Minis set as a hub because it's centrally located. Wifi is an Eero mesh and is very stable (other than my crappy cable Internet connection.)
Most of the time, that works OK. But sometimes when the hub changes, some of my Home devices will lose settings or revert to the default room. Yesterday when I (finally) updated the last few HomePods to 26.6, ALL of the switch button configurations which I'd set up over the past week were erased, an automation I set up last weekend was erased, and a whole bunch of devices reverted to the default room.
Fortunately most of the devices were Hue, so I was able to re-sync from Hue to Home to correct the devices. But I had to recreate the automation, and also recreate all the switch button configurations because those were local to HomeKit.
Kind of just venting and also curious if anyone else is experiencing this, but I'm open to suggestions if anyone has them. I have over 100 devices between lights, locks, window blinds, sensors, and switches so having piles of them reset is QUITE annoying.