I have 3 Chromecast Audios in my house, and when I create a Chromecast Group to allow any 2 or 3 of them to play at once, one Chromecast in the Group immediately stops showing up on the Devices screen on Spotify on iOS, despite still being available on Android and in the Webapp on Chrome. Casting to that missing Chromecast works just fine from Spotify on Android or the Webapp, but is impossible from iOS due to the Chromecast not being shown. Other apps on iOS, such as Emby, are able to see the missing Chromecast, and cast to it just fine. Deleting the Group immediately causes Spotify on iOS to display the missing Chromecast again.

I'm on a Premium Family plan, in the US, and I've tested this on an iPhone 7 running iOS 11.4.1, and an iPod touch 6th generation, also running iOS 11.4.1. Both are running the latest verison of Spotify as of today. Both exhibit the exact same behavior. The two devices have been tested with different accounts that are on my family plan, and both accounts also exhibit the exact same behavior. My Google Pixel 2, running Android 8.1, does not exhibit this behavior, and is also on the latest Spotify update, as well as the same Spotify account under the same family plan. My laptop (A Macbook Pro running the latest Google Chrome, and the Spotify webapp) can also see and cast to the missing Chromecast, like the Android phone.

This clearly indicates that the problem is specific to Spotify on iOS, as it doesn't show up on any other app or OS, but does show up regardless of account or device model.

Please fix this, as it means I have to constantly delete and re-create groups to be able to cast my music where I want it to be.