I would contact support directly and they don't monitor this community. 

All I can say is my ACE headphones make a noise when switching on and off even after the update. 

Do you not see a light on either? Flashing blue when switched on until they connect then solid blue?

I’ve got same problem and not able to solve it out. Contacted Sonos assistance but actually they’ve been not able to help yet. They keep saying they’re working on this and will lem me know…. I’m going to ask a substitution or a refund 

Have you upgraded the latest firmware that was released earlier this week? 2.9.3 or something. 
 

Yes and after that problem started (before the updating headphones was working properly) 

Same issue after the recent update. Sometimes it comes back though. 

I haven’t seen the issue so far with my own Ace, but it might perhaps be worth someone with the problem here reporting it to Sonos.. no doubt if there is a bug, it will then get fixed with a later update. Here’s the link if anyone with the issue want to report it and provide the Sonos Support Staff with a diagnostic report. 
https://support.sonos.com/s/contact

I have the same issue. No sound when turning on or off. Has anyone corrected the problem?