If you have hearing aids linked to your iPhone through the Settings->Accessibility menu, you are like to encounter errors during Sonos setup and Trueplay tuning.  

Specifically: When setting up new Sonos speakers, I get error messages that I need to cease using AirPlay to continue the Setup process, even when I am NOT using AirPlay.  When running Trueplay, I get error messages indicating that there is too much background noise to run Trueplay, and to try again later.

The resolution is simple - I have to turn my hearing aids off during setup and Trueplay tuning.   But the error messages are off point, and nowhere on this forum or in the product documentation have I seen this issue documented.  Hence, my post, in the hope it will save some future user some frustration down the line!

For the record, my hearing aids are Philips brand, sold through Costco, and thus very commonly used.