This seems to be a scenario that stumps sonos' discovery mechanism. In my house I have 3 wifi access points (all Unifi AP, if you care). They all broadcast the same wireless network (call it BOB). They are wired into a gigabit switch, which is then bridged to cable. This is a very reliable setup, and has strong signal everywhere; it is not wireless with range extenders, it's a big wireless network. So that's the network setup.
I have 2 Play:3 and 1 Play:5 (wonderful speakers, by the way!). They seem to only be accessible if I am connected to one particular access point, and are invisible from the others. So in this case (because I use an iPhone with its phenomenally broken base-station switching chipset) I need to be in a particular room standing near one of the speakers, and then toggle wifi on/off on my phone for the speakers to come back.
Is there a fix for this, or a known cause? Is it maybe that UDP isn't getting sent out on all the other access points, so discovery doesn't work (presuming it uses UDP for discovery the way Google Cast does). Before I purchase the Playbar + Sub combo, I want to figure out why the connectivity is flaky with the devices I do have.