I found a support case on Google that explains what I’m seeing.
I have a ST account with my wife linked. When she connects her ST account to her google home app mine starts throwing the “an unexpected error occurred…” error. If I connect mine her linked ST app breaks and throws the same error. Last one to connect wins.
Has anybody else seen this or fixed it? Right now only one person can use any of the smartthings via Google home/assistant.