Apologies, reporting the last one was totally our fault. After bootstrapping a new workstation, we activated a bogus firewall setting which denied access to googleapis.com - no wonder these requests would fail. Sorry for the noise!
Nevertheless, it was a good chance to update the theme and receive the numerous updates @sesemaya pushed since end of January (Comparing 83a7de732a13ac9f8bde60aaefbee39269c601fd...89f9f1347fb5755fdbab83f8350ebabe9d532857 · Daemonite/discourse-material-theme · GitHub). As far as we can see everything works fine, so thanks again for the awesome work you are putting into this, Maya!