Issues with finding duplicate music files

[theBelvedere]

Hi, new here -- I think MM is great so far, just need some advice on the topic of duplicates.
I keep numerous playlists (but as fully tagged album/title sets) so there is a lot of duplication of files - that's intentional on my part coming from iTunes and endeavoring to keep independant sets of music groupings that don't share files. I went cold turkey from iTunes and transitioned to a new PC - only carrying the files on portable drive over.

I noticed when MM imported my music folder and I tried to create a playlist (auto) on one of the 'album' sets in question that is also a playlist - not all the songs appear in the final list - though they are all present and in tact in the folder where music is stored. Only 388 of the 673 tracks appear - and it's random, what's missing as track number as tagged spans from 1-670

The autoplaylist is set to "any" and match to album/podcast/series... by altum title. What am I doing wrong - or is there some manner to prevent MM from skipping dupes.

Cheers and thanks to anyone that can help

[Lowlander]

Did you confirm that the Album value of the missing files as actually the exact same value you set in the AutoPlaylist Criteria for Album?