Solved my issue.
Symptom: I have 2 Google Wifi's (GW), both hard wired. The 2nd repeater (bridge mode) is about 30 feet away from car, separated by 1 drywall. When the car is searching for it, it shows up with full bars. After entering my password, I usually get "Unable to Connect", however when I do connect, I'll see 1 bar and eventually will lose the connection entirely.
Solution: Suspected my mesh complexity has something to do with it so I pulled out an old Linksys EA3500 router (released in 2012), set it up in bridge mode (802.11N only, with unique 2.4GHz and 5GHz network names) and physically connected it next to the google with a 6" LAN cable.
Result after success connectivity:
2.4GHz - Full wifi bars with instant connectivity
5GHz - 3 of 4 wifi bars with some issues in connectivity. However once connected seems to stay connected.
Sidenotes:
I disabled 2.4GHz to minimize interference and am connected to 5Ghz. 5GHz has reduced range. If it misbehaves will switch to 2.4.
Ultimately I think it's a bug with the car as all my other devices connect fine to Google Wifi. I suspect the car is confused in seeing 2 networks with the same name.
Suggestions for others to try:
1) If your router uses the same SSID (network name) for both 2.4 & 5GHz, try creating 2 different names to see if it helps. (The Google Wifi does not have this option.)
2) Setup bridge mode with a spare router - Instructions vary by model:
Usually all the old routers have a bridge mode option and if you're lucky an access point option. My linksys only had the bridge option which required me to lookup how to configure bridge to AP mode for my particular model. Here is the link I followed:
Linksys Official Support - Setting up your Linksys Smart Wi-Fi Router to Bridge Mode using the Classic firmware
Hope this helps!