Yesterday I discovered a file, supposedly one album, was actually two together with duplicated tracks. That was probably caused by earlier careless merging of the two albums (of the same work - Bach Cello Suites) some time ago. This will happen if two albums, both listed as disc 1 are merged although that should have not been the case with the Bach albums as each should have been clearly defined disc 1 and disc 2.
Anyway, the “cure” is to remove one set of “duplicated” tracks which should again create 2 albums,
This did successfully create disc 1 but disc 2 had duplicated tracks of that disc 2 album generated by this process. The first few tracks were OK, then came some duplications and further down 3 copies of the tracks appeared! So those duplications were removed and disc 2 finally appeared as it should although the phantom tracks removed had vanished altogether. This has happened before and has not been fixed in release 1.6.
Disc 2 was then relabeled as that and the two albums merged again successfully.
Not a big issue, but annoying as it causes extra editing because the phantom tracks are generated.