To get your diagnostic report looked at you’re probably best to contact/chat with Sonos Support Staff via this LINK and see what the Staff can perhaps suggest to resolve the matter.

As it’s holiday time though you may not get an answer straightaway, so you may, in the meantime, perhaps find this Support link helpful too…

https://support.sonos.com/en-us/article/reduce-wireless-interference

Hi Ken, thank for your answer. 
I’ve already tried to set wireless interferences, but the problem remains. 
 

Despite the holiday season, i’ve to do something else to get an answer  from the support  or it is sufficient to have loaded the diagnostics with the reference?

Submitting one, and waiting for them to contact you won’t work. The forum moderators in this community forum only occasionally have time to look at the diagnostic, rather than waiting for them to see, and have time to respond, you should call in. 

If you read the Diagnostics - How do they work? thread, you’ll find that Sonos doesn’t even look at your diagnostic until you call Sonos Support directly to discuss it.

Ok. Thanks you