http://musicbrainz.org/release/7d6994d0-6079-4053-bbbf-5183fc8efd3f/edit

Release's Tracklist has durations from an attached Disc ID. There is no way to copy the lengths into the associated Recordings which are all missing durations.

Related issue: can't copy artist credit changes to recordings either.

Due to this major bug, for the past year I've been recreating "complete" releases from scratch in order to merge the "bugged" release (with poor recordings) into the new release with correct recordings. (Otherwise, you'd have to manually edit each Recording one-by-one.)