I have the same issue. Have you found a fix yet?
I contacted Google support but it wasn't much of help.
I went with Ubiquity ER-X to provide routing for my house. Fixed my issue with ipv6 and gained more features which Google Wifi doesn't have such as bettr QoS management, custom firewall policies, Vlan support, etc. Turned my Google Wifi into bridge mode (dumb AP) and since I only have single puck, no mesh - it works for me. I still often do experience slowdown with wifi down to 50%. When I upgrade wifi, I will go probably go with Unifi APs since they make some of the best wifi APs in market for reasonable price.
EdgeRouter routers are good products, they have tons of features, but you may have to dive into CLI or config tree for more advanced settings. If you prefer to use UI easy to use panels, I recommend you look into Unifi line of products. For routers, there is USG, USG Pro, and newer UDM and UDM Pro but the latter two haven't yet fully matured so beware. And since these products are meant for small business or prosumers, they require more configuration in advance than simply plug-n-play like most consumer wifi routers.
If you prefer plug-in-play easy to use AIO product, you may want to use something like UI Amplifi or Eero. Heard rumors Apple is returning to networking devices market, so if you have Apple devices and can wait longer, you may want to wait for them to release new Airport routers.