I’ll see if I can figure out how to reproduce consistently. Just happened again, I haven’t noticed it when visiting other discourse-powered forums yet… it really hasn’t bothered me at all but happy to try to debug.
Update: the problem I’m seeing definitely just happens when the site is loaded from cache. Forcing firefox to make a request to the server loads fine, but anytime it attempts to use the locally cached version, I see that corrupted content error.