With both, Firefox and Chromium (both in major rls) I had a lot of connection issues with some grafics in the community here.
See here:
https://imgur.com/a/IgNkjOs
I think is a problem with your media-proxy service.
Here are some example links where I get a 404:
https://community.openconversational.ai/letter_avatar_proxy/v2/letter/s/34f0e0/64.png
https://community.openconversational.ai/letter_avatar_proxy/v2/letter/s/34f0e0/90.png
https://community.openconversational.ai/letter_avatar_proxy/v2/letter/s/41988e/50.png
Greetings suisat