I have the same mesh and I turned off beamforming on my network and the
hub display stopped disconnecting, if your router supports that feature,
turn it off, and try also disabling Fast Roaming, I have both settings
disabled, and since a week ago no ...
I totally agree with you, Google needs to provide a permanent solution
to the problem right now, it's an expensive piece of equipment that
should work smoothly, this is definitely a Google issue.
I was having the same issue but I think I found a solution, I turned off
beamforming on my router and the hub display stoppeddisconnecting, if
your router supports that feature, turn it off.