So i have several Sonos setups. I have a surround one SL pair, one play5 and a Beam plus One SL surround combined for tv. My iPad will let me airplay to all three setups but when i select any of the three setups on my iPhone (airplay sees them just fine) i get an Airplay passcode request.

please don’t tell me to reboot or re setup the sonos devices because this was done multiple times and is annoying to do. 
it works perfectly fine on iPad but on iPhone it asks for passwords. I have no password requirement setup in AppleTV or on Airplay.

Everything is setup on the same (and only) WiFi network available. And as said it all works fine on iPad why is airplay asking for passcode on iPad?