There is definitely something weird happening on the geocaching.com side. Geocaching.com is sometimes dropping the connection after it receives a request when the connection is reused, instead of fulfilling the request.
The underlying issue is actually affecting all browsers, but Firefox and Chrome work around it by automatically retrying when this happens. (You can disable this retrying in Firefox by going to about:config and setting network.http.request.max-attempts to 0. If you do this, you'll see the map randomly fail just like it does in Safari.)