Google Cast not detecting devices

Configuration
1

I had a perfectly working HA up until last night. This morning one of my automations was hung mid way waiting for a Chromecast device to turn idle from playing. I noticed the Chromecast was offline. Thought it might be a network glitch so I restarted the Chromecast and could see it on my phone and other tablets but it showed offline in HA. Restarted HA and then one my one did a full restart of the entire network. Nothing worked. Just to be sure I checked every single connection and even restarted my mDNS container which does not seem to be having any issues as all other devices can see each other on all vlans and infact the Chromecast device is seen and I can play it from multiple vlans.
As a last measure I did a full restore of a very recent HA backup. Still the same issue. What confuses me is that this setup has been running fine for months and the automation did see the Chromecast online when it started the tasks. All my other google cast devices are offline as well. So it’s not just one particular device which has this issue

Has something changed in the recent HA update?

2

For some unknown reason my avahi docker container failed to work. After a lot of troubleshooting I found it to be the root cause. Not sure why it failed in middle of the night with no updates since past few weeks. Had to kill the container and remove it as it was not picking up ip addresses from my vlans. The container was on and running. Had to recreate a new container and everything came right back up within seconds.