Sound effects have this issue as well.
Since all of the sound related assets have .txt and .lsx (i.e. XLS) file entries I would think it indeed be related to something in those files (either the files that don't preview correctly are not listed in the appropriate txt/lsx list or they have a different entry as Composer suggests for Preload - which does by it's very name sound as though it could be the issue)
I would suggest finding a file that DOESN'T play and researching it in \Public\Shared\Assets\Sound\ from the shared.pak file
Notepad++ has a powerful find feature that will check multiple files and subdirectories for you.
EDIT - I decided to poke around myself just to see. Ifan_Presentation_Music (not Idan lol that threw my searches off until I spotted it) is set to Preload=False in the editor. So does Explo_Theme_11_Dark. I guess that throws that theory out.
Both are listed in \Public\Shared\Assets\Sound\music.txt
Ifan_Presentation_Music has a duration of 48.633335 and Attenuation of -1
Explo_Theme_11_Dark has a duration of 0.000000 and Attenuation of 0.000000
So perhaps that is the issue.
