basically this happens when you're editing the release and removing one (or more) tracks in the tracklist tab. when you remove the track(s) and reorder the remaining tracks, it will result in duplicating the track positions (e.g. you have two times track 2), when moving up/down songs, sometimes it moves by 2 positions instead of 1, etc. and if you remove the last track (e.g. track 16) and move the track 15 down one position, you will end up getting one track 16 and no track 15. i assume the editor still thinks there are 16 tracks, even if you remove one of them. you can't proceed to the recordings page, even manually correcting the track numbers or using the track parser won't help. i just random tested on this release: http://musicbrainz.org/release/bd30f0e4-7cfe-4df2-8ede-e75870f74e94 (see attached screenshot), attaching also two of the talks on irc.

http://chatlogs.musicbrainz.org/musicbrainz/2012/2012-08/2012-08-15.html#T17-44-51-790889 (only my initial post)
http://chatlogs.musicbrainz.org/musicbrainz/2012/2012-08/2012-08-16.html#T00-28-13-54255 (reosarevok helped also with testing and confirming, the discussion lasts till 00:37:56)