Images in artifacts are not working

[thermusmaximus]

I'm running LibreChat via Portainer on an ubuntu sever in my LAN. I use Nginx Proxy Manager as a reverse proxy (which might be causing the issue). I tried generating a few sample artifacts to see what the possibilities are, but all images included in the artifact fail:

I'm not entirely sure of where I can even start looking for the problem. Does anyone have any ideas?