Airplay 2 & Homepods

Controlling volume on HomePod and speakers (airplay 2) via Siri used to be possible - then it stopped around the end of last year with what I think was a HomePod update. Here is the full description I posted elsewhere. Others have confirmed with me that they have the same issue. I have a HomePod and speakers powered via an Airport express in my kitchen room on HomeKit. I can tell HomePod to “play” some playlist from Apple Music “in the kitchen” and it plays on both HomePod and ap express. However, if I say lower the volume in the kitchen - I get an error from Siri saying there was an error adjusting the volume. The HomePod will adjust, the airplay 2 speakers will not. I can adjust the manually from my iOS device however.

full description of my issue and measures taken:

Airport Express and Homekit behavior change (volume via Siri)

Been pulling my hair out trying to fix this issue - anyone else seen anything similar?

* Airport Expresses - with 7.8.1 firmware to support Airplay 2

* Worked flawlessly for over a year

* Volume issue: I have an orig Homepod & Airport Express setup in Homekit in the "kitchen" room

* I used to be able to say "Hey Siri - set the volume in the kitchen to 40%"

* both the homepod and the APExpress would change together to 40%

* In the past month, something has changed - any changes to the the room no longer adjust the APExpresses

* Siri no longer will adjust the "kitchen speakers" (APExpress) independently

* "Sorry, there was a problem"

* I can adjust them independently in the home app, iOS 14.3, but not together

* I can adjust them independently in the iTunes - when i select to control the HomePod for example, but it doesn't control both simultaneously (it used to)

* I can adjust them together or independently via the "Control Other Speakers & TVs" in the iOS control center, iOS 14.3

I've tried:

* deleting/re-adding them (APExpresses) to Home App, and the kitchen

* restarted the 4 ATVs designated as the homekit hubs - *many times*

* restarted APExpresses, Homepod, router, switches - *many times*

* AP Expresses are all directly connected to network via hard wire

* I don't have any vlans or other network fanciness set up

* I do have both 2g & 5g wireless enabled - and have found some seemingly unrelated issues with Airplay 2 in doing my research

* FYI, I added a new HomePod mini to the mix in the past month - which shares the timeframe of these new issues

* FYI, my MacOS version is a bit old (10.14.6) and I realized Home app doesn't support everything my iOS Home App supports

* I use both desktop and mobile home app to setup/configure/control