Song tracks are not downloaded properly from iTunes Store: they are not added to the playlists, and eat disk space

Hi,

Yesterday I wanted to upgrade my wife's iPhone (5, 16 GB) from iOS 7.0.6 to iOS 7.1.

She had only 500 MB of free space, and 1.9 GB was needed, so I decided to temporarily remove a number of songs from her music library.

After this operation there was 2 GB free, and the upgrade went successfully. After the upgrade there was still 2 GB free.

Then I wanted to download the songs again, and here something went wrong:

I went to iTunes Store > More > Purchased > Music, and clicked on "Download all".

When the download process was completed, there was about 500 MB free space, but I noticed that some of the tracks, and even a complete album, were actually not in the playlists; in another album only one of the 30 tracks or so was downloaded. So I went again into iTunes Store > More > Purchased > Music, and indeed some of the tracks were still marked as "to download", with a little cloud in front of them.

When I tried to click on one of these little clouds to download a given track, the track seemed to be downloaded, but as soon as the download was finished the little cloud reappeared again, and the track wasn't added to the playlists.

I tried to repeat that process a few times, until I noticed that there was now only 90 MB of free space.

I then tried to download one more track that was 10 MB large, and after this there was only 80 MB of free space.

So it seems that the tracks are indeed downloaded (and downloaded again if I click again on the little cloud) in a place where they use disk space without being otherwise accessible.

What can I do to:

1. download the tracks correctly so that they appear in the playlists?

2. clean up the space that was wasted?

Many thanks in advance!