Yes.. others have complained about the low volume… but it falls on deaf ears at SONOS. 

Hi @CantHear 

Welcome to the Sonos Community!

The next time this happens, I recommend you submit a support diagnostic while playing and record the number given. Then, at your convenience, please get in touch with our technical support team who have tools at their disposal that will allow them to give you advice specific to your Sonos system and what it reports - just let them know the number you recorded.

It’s possible that the speakers are attempting to protect themselves from overheating - especially if you are in a hot country. This is just a guess - the team should be able to give you a more definitive answer.

I hope this helps.

Or maybe it falls on deafened ears at the users.