Although you’ve now returned your Bluesound devices, I wanted to add that you are not alone in these issues. When I had Orbi, I had Bluesound players randomly drop off the controllers (iOS, Roon and iMac) and only rebooting the players would bring then back (sometimes not even then). Yep, that gets annoying over time.
I moved to Plume Wifi, and things have been somewhat more graceful. If the players decided (using their own crazy logic) to move themselves to a different mesh node, they would still drop off the controller apps; Plume had to disable client steering for all Bluesound devices. Bluesound logic (wifi, we are talking) is a bit mad, the players will choose to connect or move to a much weaker pod (plume call their nodes ‘pods’) and then they would just drop off the network. I have things mostly stable using plume wifi (I only ever group in the bluos app and not Roon). Now, if they do ‘move around’ wifi mesh nodes, they will, at least, stay visible to the bluos controllers. The players would then still have to be rebooted to returned them to a node that can give a better signal to the Bluesound player.
I have always suspected that Bluesound’s wifi firmware to be somewhat troublesome, and I don’t think they like mesh systems very much either. Hardwire the things and they are perfect. Dropping players is rather too frequent on their support community and their forums. Then again, I think Sonos has similar trouble, and that’s why their players can create their own mesh.
When I can, I plug Bluesound into the ethernet port of the satellite mesh nodes (pods). And those plugged in cause no trouble at all.