I would recommend that you submit a system diagnostic within 10 minutes of experiencing either problem, and call Sonos Support to discuss it.

There may be information included in the diagnostic that will help Sonos pinpoint the issue and help you find a solution.

When you speak directly to the phone folks, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Update. 

Followed your recommendation this evening.
 

Sent a diagnostic immediately following a reoccurrence of the issue, called Support. Spoke with Mary, went thru the usual one goes through on a support call, “it’s a known issue”. And…sending me a new Arc! Too cool . 

Interesting. It’s not a ‘known issue’ I am aware of, but I’m happy they’re replacing it for you. 

Apparently I’ve been living in ignorance. Not on this forum much. Just learned of the infamous “pop of death”. Per Ars Technica that problem has been fixed with a software update. 

I wish I had questioned the support person more throughly but I was so excited they were replacing the ARC it didn’t occur to me. She did mention ATMOS several times during our session but not a word about a software update. 

I purchased the ARC last March. It doesn’t really matter but I wonder what sort of hardware malfunction we’re looking at?