This is more of a solution than a problem I’m presenting. For quite some time, I’ve had issues with Google Chromecast devices suddenly becoming unreachable and not responding to cast commands, such as playing internet radio. This is particularly annoying when casting to a Google speaker group. The only solution used to be restarting my Homey PRO.
I’ve finally identified the cause of the problem, which is the overload of the internal mDNS network on my LAN. mDNS is responsible for discovering most cast devices, including Chromecast speakers, Sonos, and other devices. To resolve this issue, I installed an mDNS repeater on my network. I am currently running it on a Synology NAS, but it can also be run on a regular PC.
I hope this helps others who are experiencing similar issues, often due to having too many devices on their network (mea culpa 
).
Jo
