Hi, this issue is related to having an Amazon Echo Dot on your network connected to the same Spotify account as you are using on your iphone.
Open Spotify App, start playing on your iPhone, switch to Spotify Connect supported device (not the Amazon Echo). Streaming starts and plays without issues.
When you open the Spotify app once again it somehow changes the output and stop playing. The output is reset to the iPhone. This also happens when you are trying to change the audio by clicking the bottom section where it shows the connected device. The app goes to the screen where you see the slider but immidiatly disconnects the Spotify Connect device.
I'm using Spotify and the Spotify Connect device for some time now and this issue has never come up. It's also not present if I disconnect the Echo dot from the network, just by unplugging the power.
It's also not behaving like that if I'm using the Echo dot as the streaming device. I can go in the app whenever I want change the volume, change the song. It just continues.
But thats not what I expect when I'm using other devices to stream to.
Do you know if this is an know issue please?