Offline Sync not working on all playlists (< 3.333 titles)

[JPx]

Hi!

Last night some newly added playlists stopped downloading tracks into offline mode on my iPad3.

I've selected about 10-15 new albums and added as playlists, then activated for each the "download playlist" option. 

Most are now available, but a few, incl i.e. Keith Jarret - "The Köln Concert" or Melody Gardot - "Live from SoHo" simply do not download the tracks. They show the green arrow in the left upper corner of the cover, but nothing happens.

I've deleted and re-added those playlists again today, still no success....

Btw, I am far away to exceed 3.333 tracks, far.....

Anything particular with these tracks that prevents syncing?

Thanks