One of our users recently tried to access the StackExchange chat through chat.crypto.stackexchange.com which depending on a few things will either yield a domain miss-match certificate error or will yield you a page showing you an error:
Server Error in '/' Application.
Description: An exception occurred while processing your request. Additionally, another exception occurred while executing the custom error page for the first exception. The request has been terminated.
Note that for any other unmapped site, like
potato.meta.stackexchange.com you actually get an error that says "couldn't find this Q&A site" so this is apparently a bug in the chat server software (or at least an inconsistency).
As this issue also covers other sites like chat.security.stackexchange.com this is posted here on Meta.SE.
While I see why this is a low-priority issue, a fix to this would be as simple as un-mapping the DNS for chat.site.stackexchange.com I suppose?