Everything is duplicated

[SolihullRog]

I recreated my database about a month ago, by doing the following:
Under Movies, I created a folder called Other Playlists.
I then moved all of the standard playlists, as supplied by Mezzmo, under that folder.
I did all my own work outside of 'Other Playlists'.

I have come to discover that 90% of my entries in all of the standard playlists show duplicates of every entry.
See attachments for (1) Movies beginning with 'A', and (2) actor is Clint Eastwood.

How might this have occurred and how do I rectify it?
I don't want to recreate the database, and all of the playlists, yet again.