My setup is a follows

A BT Smart Hub 2 setup as suggested for chromecast. I.E.:

• Router is within 10-15 feet of your Chromecast.

• Enable: Universal Plug and Play (UPnP), multicast, Internet Group Management Protocol (IGMP)

• Disable: AP/client isolation, virtual private networks (VPNs), proxy servers, IGMP Proxy

• Please note, each router and its settings are a bit different. Contact your router manufacturer for details.

• Turned off the Smart Setup feature in the router settings and reset the Chromecast.

I have the wifi on this turned off on the Bt router as it's down in the garage which is below the house.

We have 3 TP-Link EAP access points controlled by their Omada software (Version: 3.1.4). So the ssid is the same and set to channel 3.

EAP110(EU) 1.0/2.0 1.3.0 Build  Rel. 74831

EAP110-Outdoor(EU) 1.0 1.2.0 Build 20180418 Rel. 74942

EAP115(EU) 4.0 3.3.0 Build 20190301 Rel. 37101

Most of the Google chromecast audio pucks are in the garage with an AP (EAP110(EU)) 3m away, two are in other rooms close to other APs.

I have the latest firmware on everything including my android Samsung S8 phone.

So everything is on the same network on the same subnet. As I roam around the house the phone obviously moves from one AP to another if it needs to. This seems to be the issue. If I'm attached to the same AP (EAP110(EU) the garage based Chromecast pucks are,  I can see all of the pucks including the ones attached to other AP (EAP115(EU)). However when I move to another AP (EAP115(EU), I can't see the pucks in the garage only the two attached to it. Moving to the (EAP110 - outdoor(EU)) I can not see any.

I'm happy to try anything, I really don't like the BT SmartHub 2 and may change that (any suggestions fttp?)

TP-Links new AP’s have Seamless Roaming, and Mesh should I change to  them?

I would like the household the ability to roam and control from their telephones.