Cannot merge or delete duplicate files

As of a few months ago, some newly imported albums create a second album with a single track. The single track is alway a duplicate track from the main (full) album. I’ve tried every combination of merge, delete, rebuild, restart, but no matter what I do, the duplicate remains. This screen shows 3 examples, but let’s focus on the red Bicep album in the lower-right corner:

Screen Shot 2021-06-05 at 11.31.52 AM|663x500

This screen shows the internal storage on my Roon Core (NUC). As you can see, everything here looks fine:

Screen Shot 2021-06-05 at 11.41.24 AM|690x255

Any idea how to resolve these duplicates?

Have you possibly liked the single track in a streaming service connected to Roon?

No, not using any streaming services. Only local files.