Sorry for the confusing title.
I just experienced the following small inconcistency using the android app together with a Chromecast Audio on a Samsung S6 Edge.
1. Select a song to play in the android app - music plays from phone
2. Select the chromecast device from within the "Devices" page in spotify (press the small icon at the bottom of the screen to get the devices page).
3. Music continues coming out of the phone while casting is initializing
4. The chromecast audio connected beep is heard through the chromecast audio speakers - music is still playing from the phone.
5. I skip to the next song in the playlist on the phone - this starts playing on the phone.
6. The previous song (the one selected in 1) starts playing on the chromecast audio a few seconds later.
I had expected that the chromecast audio should play the song selected in 5, not the song selected in 1.
Spotify Version 18.104.22.1688
Samsung Galaxy S6 Egde Android 5.1.1