I have 2 Chromecast Audio devices. These work intermittently on my HH5 - sometimes don't stream at all, sometimes only one streams. I can usually get them to work after rebooting (hub, chromecast device, or cell phone) but it's a frustrating process.
I googled and found there were issues with certain firmware versions on the HH5. I'm out of contract and stuck with old firmware so I didn't play around too much and decided to buy an HH6 which arrived this week.
I'm having the same problems as I had on the HH5. The HH6 is on firmware version SG4B10002244. The chromecast audio devices are on the latest preview firmware (1.23.82244).
Having read these forums I have tried the following:
1. Disabled smart setup (it remains disabled)
2. Split the networks and connected the chromecasts to either 2.4 or 5
3. Assigned fixed channel numbers to both networks
4. Tried each of the 3 wireless modes.
None of the above seems to work - chromecast audio still only works 'sometimes'. Sometimes I'll get the connection sound but then nothing plays, sometimes nothing at all, sometimes just the disconnect sound. It does seem to be worse if I'm casting to a group (2 devices). I also have a chromecast video and I've never had a problem with that. The audio devices have no problem connecting to the hub or staying connected (status light is white and I can see them connected on manager)
I have 3 Chromecast Audio devices and a HH6, I have exactly the same problem. I find connections unreliable and intermittant exactly as you described.
Some times you can connect after a few failed attempts, once connected I find that things become more reliable !! at least for a while.
I also find if I want to use a group its best to try and connect to each device individually, when you achieve this, the group then "probably"works.
Most times I do not reset the hub or device, I just keep Casting/Stop Casting until I get a connection
When I posted my last message I had not used my Chromecast Audio devices for a while, your post made me switch them on and check their firmware. They all updated to the same firmware version as yours and the result is terrible.
Group mode is now almost completely broken, one Chromecast works fine on its own but "pulses music on and off" when in a group. I tried swapping this device over and the same thing occurred so its something regarding the location !!
(Never seen this particular problem before the update)
I Googled the firmware version 1.23.82244 and it looks like Google have screwed up again.
I was going to buy a Google Home device this weekend but have now lost faith in Googles software department. Maybe if they restore reliable Chromecast operation I will think again.
About a year ago my Chromecast Audio devices were rock soild - totally reliable operation - some progress.