Seems odd, certainly. Makes me wonder about possible IP address issues with your local library device, and not your speakers themselves. 

Try powering down this device, then reboot your router. Give the router a couple of minutes to recover, then plug back in your local library device. Give it a couple of minutes to come back up, then test.

However, if this doesn’t resolve the issue, I would recommend that you submit a system diagnostic within 10 minutes of experiencing this problem, and call Sonos Support to discuss it. But don’t post the resulting diagnostic number here, they get sensitive about GDPR.

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 Support staff, they have tools at their disposal that will allow them to give you advice specific to your network and Sonos system.

Thanks. I've done the rebooting etc. I literally don't have the time nor the inclination to submit diagnostics and contact support. 

I'm not at work. This is just grinding me down.

If the reboot initially helped things reserving static IP addresses for all Sonos devices may be a more permanent solution. See your router’s DHCP settings page to do that.

I did another reboot of everything while I went out earlier, and I managed to play an album at the first time of asking. 

I'm still getting the Something Went Wrong error when just navigating around the library in the app though. 

Is anyone else getting this?