Unfortunately, A9 built-in chromecast remains very unstable for me. For some time now, it stopped completely to work (i.e., A9 chromecast cannot be identified by the Google Home App and also not by other apps that access it via chromecast). Unplugging it from power also does not help.
The integrated airplay and even spotify connect work. So, it is not a wifi issue. Just the chromecast built-in feature is unstable / no longer working at all.
Any more thoughts?