Chromecast (Google Home) on Orbi -- not able to see all speakers

My wifi devices cannot see all of my Google Home devices in order to Chromecast. Depending on whether I'm connected to 5/2.4 GHz or the base station/satellite, I see a different collection of Chromecast speakers and groups, but never all of them at the same time. Casting only works most of the time. Re-setting up the speakers often leads to "your phone is unable to communicate with the Google Home" errors and a link to help article on AP isolation, though they can all connect to the wifi just fine. Repeating the setup multiple times eventually succeeds but the problem of not being able to see all the speakers persists.

I've tried getting them all on the 5 GHz band by disabling Fast Roaming, I've tried disabling daisy chain / MIMO / beamforming, all with no success. Everyone seems to indicate that Google Wifi works great, so I'm assuming it's a bridge setting or something buried in Netgear that's causing the problem, rather than an inherent problem with mesh networks.

Extensive Googling hasn't really turned much up. Does anyone have any tips? I'm on firmware 2.1.4.10.