2 of 3 Era 100 consistently do not show up in Mobile app

I have 3 era 100s. all 3 consistently show up in the Windows app (always there) but 2 of the 3 rarely show up in the Iphone app both in control panel Airplay and on the app system. Both will work with SVC but not available to cast music from my Iphone. Unplugging and restarting is only a temporary fix and before long the speakers become unavailable again.

I haven’t done a recent reset but after the last time I reset, the problem arises again soon thereafter. I’m on a newer Netgear mesh router where one of the hubs is only 2 feet away from one of the Era 100s not visible. Otherwise my WIFI is rock solid.

My Sonos Roam always appears available along with the Arc and Port.

My Sonos arsenal: 3 Era 100s, Arc, Sub Mini, 1 Roam, 1 Port.