I have 3 different Google devices, a Chromecast audio, Google home mini, and a Google home hub. When trying to cast Spotify to any of these devices, it won't usually cast the first few times I select the device from discover devices. When I do get a successful cast, it'll usually stay connected for the first few songs, and then disconnect or un-sync from my note 8. I won't be able to control the music from the app anymore but the music will continue playing on my Google homes or on my stereo via chromcast audio. Force stopping the app sometimes works and it will cast for longer than it normally does, but then it will revert to the un-syncing I mentioned above. All devices and app are up-to-date. I've noticed it will sometimes switch the casting device from my phone to my MacBook if I have both open.
Looking for any solutions as this has been an issue for awhile now and is getting frustrating
( Samsung Galaxy Note 8, Macbook Pro late 2016)