Are any of the drivers blown or dead? Stick an ear up close and listen to each one.

I suspect you have this issue:-

Ignore the answer as this is a known issue and is not resolved.  We are all hoping the next release sees a fix.  I nearly went to the extremes of buying a replacement speaker!

Then I physically swapped the speakers over and then unpaired an re-paired them to get the L and R channels correct and found the Left channel (on the previous right channel) was still the louder.  Then tried factory resetting both, and performing Trueplay Calibration, yet still the L channel was louder.  Turn off Trueplay and it was fine, albeit the overall sound was booomy(the reason I was using Trueplay was it made the sound so much better).  Frustrating!

I don't think I have Trueplay. I don't see it in my app. I use Sonos S1 as all but one of my speakers are older models.

John

@Stanley_4 Your suspicion was correct. I have a dead driver. Now to see if it can be repaired…

Thank you!

John

Hard to find a repair shop, Sonos if contacted will sometimes offer a nice discount if you buy a replacement though.

If you have a local shop that can do the repair ebay and the like usually have “parts only” Sonos devices that have died. Getting one with good drivers and dead electronics would be ideal.

Double check this. I nearly spent over £300 that was not needed. 
 

physically swap the left and right speakers.   Then do a factory reset on both and then re-pair them. Then check which speaker is faulty. If it has moved sides then it’s a speaker fault. If not it’s a software issue.