I use my Chromecast / Google TV almost daily, and usually just use the remote & on-screen UI (no casting). It's hooked up to my Sony Bravia 4k TV, the TV is connected to a Sony soundbar via optical out, and I would say 95% of the time it works like a dream. Both the TV & soundbar are 7+ years old, so I have a second remote to turn the soundbar on. There is no sound when the soundbar is off (obviously) -- no sound comes from the TV itself.
5% of the time, totally randomly, I will turn on the TV and there is nothing I can do to get the sound to work. I will restart the chromecast, restart the TV, turn off the soundbar, fiddle with the sound setting, make sure the chromecast is turned on before the soundbar (unclear if this matters), once I went so far as to factory reset the chromecast and I still have this issue. Whenever this happens I just give up on my TV for the night and usually the following evening it's working perfectly again.
Any ideas as to what's going on?!