I found a possible issue regarding coverart-based selection.
In my music store there are two works of Maurice Ravel ("Boléro", "Pavane pour une infante défunte") in two different interpretations.
Let's consider "Boléro":
Tags of first FLAC:
Tags of second FLAC:
Thumbnails for both are generated and present. Both works can be selected via library view but only one of them via coverart-based selection. The other thumbnail seems to be "orphaned", clicking on the thumbnail lasts undefinitely.
klassikmann