We currently have one Echo (4th Gen) and two Echo Dots (4th Gen) inside the house in various rooms. In the past 10 days, or so, we have noticed the Echo volume occasionally fading down and returning. The Dots also do this, but recently they just started to totally shut off. Please note that this only happens when they are used in a group from the Alexa App and it doesn't matter what music stream I am using -- i.e., Sirius or Amazon music. When activated individually, no issues are noted. I have unplugged all devices several times, as well as restarted the network hubs without any success in correcting the problem. Anybody out there have any idea on what is going on or how to correct this to reuse the groups? Oh yes, I have deleted and reestablished the group several times without any luck!!!! Help!