I saw several reommendations to PM Comcast_Support for additional assistance.
Once or twice a day, I will notice my iPhone, or the kid's Chromebooks having trouble resolving websites. It gets stuck on the resolving host step. After a few seconds or minutes the problem goes away and sites start loading again.
While the problem is happening, DNS resolution (nslookup) fails, but direct pings to IP addresses work.
I have tried various combinations of DNS settings in the Google Wifi router (ISP defaults, 220.127.116.11, 18.104.22.168, etc.)