While editing a release with a discid (http://test.musicbrainz.org/release/fc60c2d0-aec2-484d-b8e6-6b518e62c90c/edit),
In the "Tracklist" tab, I just clicked on Guess Case, and then on Next.

I got the following errors:

• The length of track 1 cannot be changed since this release has a Disc ID attached to it.
• The length of track 5 cannot be changed since this release has a Disc ID attached to it.
• The length of track 8 cannot be changed since this release has a Disc ID attached to it.
• The length of track 9 cannot be changed since this release has a Disc ID attached to it.
• The length of track 2 cannot be changed since this release has a Disc ID attached to it.
• The length of track 3 cannot be changed since this release has a Disc ID attached to it.
• The length of track 4 cannot be changed since this release has a Disc ID attached to it.
• The length of track 6 cannot be changed since this release has a Disc ID attached to it.
• The length of track 7 cannot be changed since this release has a Disc ID attached to it.
• The length of track 10 cannot be changed since this release has a Disc ID attached to it.
• The length of track 11 cannot be changed since this release has a Disc ID attached to it.
• The length of track 12 cannot be changed since this release has a Disc ID attached to it.
• The length of track 13 cannot be changed since this release has a Disc ID attached to it.
• The length of track 14 cannot be changed since this release has a Disc ID attached to it.

Two issues:

• I haven't changed any track length, so I shouldn't get this error
• When a discid is present, it should be more obvious that track length can't be changed, e.g. track length from the tracklist should not be parsed and then updated in the preview