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I have five Amazon Echoes in my home, with Spotify as my default music player, and all five Echoes are in a multiroom group ("Everywhere").

I have a strange issue where using Alexa voice commands to initiate multiroom playback ("Alexa, play suchandsuch playlist everywhere") only works correctly (i.e., plays out of all 5 Echoes) when spoken to one out of the 5 Echoes.  For the other four Echoes, if I speak the command to one of them, music does start playing, but from every Echo in the group except the one I spoke the command to.  

Each Echo works perfectly fine when used individually, and using Spotify Connect from a smartphone works perfectly as well with the group.

I even experimented with create different groupings of Echoes, and it seems like in any given group, only one Echo can correctly start audio using voice commands.

Anyone else experience this?