Cover does not display properly

[simoncn]

The speical treatment of ", disc n" in the album title is described in this section. MinimServer automatically removes ", disc n" from the album title value, so all discs are merged into the single album "Bach Cantatas [Gardiner]" and do not have DISCSUBTITLE values. Because each disc does not have a DISCSUBTITLE value, it cannot have its own cover art file.

The simplest solution is what you have already tried: change the album title so that it doesn't end with any of:

[disc n]
(disc n)
, disc n

Each disc will then be treated as a separate album, like your other box sets.