Spotify keeps dropping

Doahh

I have a Polk React soundbar in a multi-room setup with several Echo devices. Spotify will play but stops randomly. There is no pattern to the stops which will cut out half way through a track. This happens up to every twenty minutes but maybe 5-6+ times a day. I have to ask Alexa to "Resume"to listen again. I think this only happens when the Polk is in a speaker group but I'm still testing that. The Spotify app simply shows the track is paused. I have deleted the speaker group, reinstalled Spotify and restarted the router and Echos. Does anyone have any advice please?