Which controller are you using, S1 or S2?
What is the source of music?
What does the Room name for the pair of PLAY:1s show?
S2 controller
Source of music is Sonos Radio
Room name is Gym
Submit a diagnostic and check with support.
Normally speaking, there’d be something after the name Gym, at least on the Settings> System page. That’s the information I’m after. For instance, I’m playing right now Desk (L+R).
You’re current with the S2 controller , and firmware on all the speakers? When you run Settings>System>System Updates, does anything happen?
The room says Gym (L+R+Sub).
The update says No Update Required. I also have Auto Update turned on.
OK, that’s what I was looking for. Which is bad, unfortunately, but a key indicator. At this point, I’d recommend that you submit a system diagnostic within 10 minutes of playing something with some bass in it, and call Sonos Support to discuss it, as @nik9669a suggested.
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 Sonos system and network.
What should it be saying out of curiosity?
It should be saying what it is. If it hadn’t had the +Sub, that would have suggested an issue with the Sub not actually being bonded, in some way. That’s why I’m supporting @nik9669a ’s suggestion that you need to contact Sonos support.