I noticed on I site I use a lot suddenly images were not loading properly. This happens sometimes with this site so I did not think much about it. But then I notice no other users are complaining about it, and notice the images load ok in Chromium.
I double checked about:networking in Firefox and notice it's trying to do the IPv4 lookup , which fails. But Chromium does the IPv6 lookup, which worked.
After I turned off DNS over HTTPS and restart Firefox it worked ok. Before restarting Firefox it did not work.
Settings > Privacy & Security (scroll to bottom)
