Due to a forum thread http://forums.musicbrainz.org/viewtopic.php?pid=22628#p22628 I got aware of the following bug (At least I think this isn't intentional)

When I make the following lookup it's looking good:
http://musicbrainz.org/ws/2/recording/6bd68504-40cd-43f7-bd79-f1374d31ffad?inc=releases

The same lookup but I include discids or media:
http://musicbrainz.org/ws/2/recording/6bd68504-40cd-43f7-bd79-f1374d31ffad?inc=releases+discids
http://musicbrainz.org/ws/2/recording/6bd68504-40cd-43f7-bd79-f1374d31ffad?inc=releases+media

Now the <text-representation> and the <barcode> elements are missing.

I made some random tests with other recordings and tested lookups for different entities like artist, release and so on. All of them seemed fine to me.
A simillar request done as a browse looks good too:
http://musicbrainz.org/ws/2/release?recording=6bd68504-40cd-43f7-bd79-f1374d31ffad&inc=media

(Looks like the initial problem of that thread is already covered in another ticket http://tickets.musicbrainz.org/browse/MBS-5847 and this one might too.)