That suggests one of two things. 1) the server from Amazon music is having a hard time responding to the Sonos’ speaker’s request for music, or 2) that there’s a difference in the bandwidth required (is Amazon HD music, perchance) and your Sonos system is running into headroom issues when trying to get enough bandwidth from your router to play the stream. Might be worth double checking the wifi interference FAQ, as there’s lots of good information there, even if it turns out to be 1) and not actually 2). 

I am having the exact same problem.  I’ve gone in circles with this.  Plenty of  bandwidth to the modem, Velop router.

Bandwidth to the modem isn’t the significant factor, it’s the bandwidth (and potential wifi interference ) between the router and the speakers, and between the speakers, if grouped, that is most frequently the issue. 

Thanks for the input.  I have deleted all groups in an effort to isolate it.  I have moved things around and will dig further into interference.  Ive already set the channel, etc.