So it may be different with me since I don't use the homepods as TV speakers anymore.
When I ask siri to play everywhere, it doesn't play on the apple tvs in those rooms, it ONLY groups the homepods. But I noticed when paired with an apple tv, it would often turn the tv on and start playing or it would flat out refuse and say "sorry something went wrong". The temp fix would be to restart apple tv and homepod, but it would hit the bug again eventually.
It seems to really struggle at times unlinking from the tv (even when the tv is off since I dont think the apple tv is ever really 'off') and grouping with the others. It will also more frequently fail if you do the request with that homepod vs the request coming from another room which then links it (so another homepod being the controller).
For me, the sonos beam (gen1) or my other airplay 2 devices never group with the "play everywhere" siri command. I'm not sure why tbh, they will link if I do it manually but it always just prioritises the homepods.
I just assign multiple zones and then assign the rooms. So e.g. I have a "shower zone" and I can say "play this in the shower" and it will play bedroom/hallway/wardrobe rooms and it does so much quicker than the "play everywhere" command.
Thanks for letting me know your setup, so it looks like the bugs are still there even on gen2 homepods and the mini's. It has to be 100% software related then not just the apple watch chip in gen1 being too slow to cope.
I'm really hoping the new rumoured siri in ios18 is also included in the homepod OS.
I love my homepods as speakers, but the bugs are far too frequent, failing to complete requests 40% of the time.
I have now pretty much cracked it.... but in a very roundabout way.
So, what I noticed is that using SIRI on the phone works far more reliably than addressing the HomePod directly.
So I recently got used to picking up my phone and saying 'Siri play music everywhere' etc and more often than not it would work fine including SONOS speakers. It seems invoking airplay multi room music is far more reliable under iOS than HomePod directly.
That said, I have created a robust and so far 100% reliable workaround.....
I usually listen to RadioX in the morning... and when I wake up I ask my HomePods to 'play RadioX everywhere' - this rarely works with various errors and speakers not connecting... and dont get me started on try reliability of using the alarm function on the HomePod with a Tunein radio station as the alarm audio!
So, noticing that the phone works better..... I created a shortcut on the phone... and that shortcut has the following simple steps:
1. Set the airplay destination to 'bedroom'.
2. ADD the hallway to the airplay destinations.
3. ADD the kitchen to the airplay destinations...
.... ADD, ADD, ADD one step per destination until you have all the devices including homepods and SONOS speakers.
final step: Play RadioX
Next, I automated the shortcut - running it every weekday morning at 7am.
Now, the radio starts reliably, and on all my speakers throughout the house and so far hasnt glitched once.
So, moral of the story is... dont rely on Siri on the homepods for multi room music.... for now it's still a bit rubbish.