I compiled Mediatomb from git and as I see, all albums are now in the database just "object.container" objects instead of "object.container.album.musicAlbum". This has the effect, that the albums are not sorted by track number anymore. In the latest stable version this worked fine.
BTW: Artists are also just "object.container" instead of "object.container.person.musicArtist
Regards,
Marc".
I have created a patch to fix this problem. Seems to be just one line in js_functions.cc that is setting the container type to a value which had just been freed with JS_free, causing it to later default back to object.container.