That’s odd. When I pull up AirPlay 2 on my Apple devices, I only see Sonos Ones as being available targets, and none of my PLAY:1s. Which for me is expected, my understanding is that the PLAY:1 doesn’t have the electronics to receive an AirPlay 2 signal. I think I would recommend that you submit a system diagnostic within 10 minutes of recreating this, and call Sonos Support to discuss it. 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.