See the track artists for http://search.musicbrainz.org/ws/2/recording/?query=rid:665b5a77-2e07-48dc-a780-e2a43467c693&offset=0&max=50&fmt=jsonnew&dismax=false
The artist-credit section is inside another artist-credit section.

This seems to happen every time the artist credit section is included for a track (i.e. when the track and recording artist credits are different, since it's omitted when they're the same).

Our JSON for the other direction, https://musicbrainz.org/ws/2/release/e9d76765-8488-46ac-bc8d-d5d08cd7c8dd?inc=recordings+artist-credits&fmt=json (i.e. from the release to the recording) doesn't represent it like that.