Whan adding a new release via Picards "Manual Lookup" function, track lengths are automatically added to each track. When editing tracknames with the basic tracklist editor, the track lengths are replaced by "?:??" (and I was unable to add them again). (ModBot will add the lengths a couple of hours later, but still it seems buggy that they are removed by the basic tracklist editor).
Steps to reconstruct this:
1) Do CD Lookup in Picard, select "Manual lookup".
2) Search for release, then select "Add a new release".
3) Enter some artist, then go to "Tracklist".
4) Select the "basic editor"
5) Observe that track lengths are all there.
6) Enter some names for tracks.
7) Observe that track lenghts of edited tracks are gone.