Alexa won't consistently play Apple music on my whole house group

I have one Echo Plus, two Echo Dots, and one Echo Show. For the past 2-3 weeks when I try to play any of my playlists I set up in iTunes on the whole house group that includes all of the devices listed, Alexa will play a few songs successfully, then either stop completely or stop only on one or two of the Echo devices. It almost seems like a buffering problem maybe? Sometimes (not always) when I tell Alexa to pause or stop, wait 30-60 seconds, and then resume or tell her to play the playlist again it clears the logjam and will play for a few songs and then the same issue. When I try to play a playlist on a single device, no issues. Also, not sure if this is related, but I cannot get Alexa to turn on Shuffle mode when I try to use it with my playlists, even if the playlist is relatively short.