Lost album covers:
Two large pockets of loss may arise. In the first, the covers of the songs in the cloud suddenly disappear: it is most often covers repatriated with the Get album artwork, while those added by hand are preserved. Sometimes it is a temporary problem that goes all alone in order, but if it will accept a less aesthetic presentation, since the Get Album Artwork does not work with songs in the cloud.
In the second case, it is the local covers of songs that are deleted. Another variant: you change the cover of a song by local, and the former comes when syncing with iTunes Match. Again, there is unfortunately not much to do, although some have managed to find their covers by disabling iTunes Match holding down the ⌥ then reactivating.
In general, it seems that the covers inserted as ID3 tag (by dragging an image file in the box Illustration of the Info tab of the info panel) are less sensitive to these problems that covers associated with the Get illustrations album. It is therefore not impossible that the problem comes from the timing of the iTunes Album Artwork folder - about whether Apple will decide to settle ...
My metadata is lost:
Variant of the problem of pockets, overwriting metadata iTunes Match. It may happen that some pieces are downright famous for iTunes Match, for no apparent reason, or that all their metadata are removed. It does not seem to be a file corruption problem.
In general, refill and metadata sync iTunes Match is enough to get things in order If the problem affects many pieces, do not hesitate to use an application like the excellent Music Brainz Picard to automatically fill metadata.
iTunes Match has duplicated my playlists:
Another classic, duplicate playlists - sometimes hundreds of times! In our experience, the problem seems to be related to the loss of which would cause a runaway network during synchronization. These playlists are empty extra: a simple script will remove quickly while keeping your playlists original (and full).
If none of the previous manipulations has worked and that your problems were not resolved in themselves (as is often the case with iTunes Match), there are only two solutions: resetting iTunes Match and updating your iTunes library.
Reset iTunes Match:
Simply put: there is no "reset" button on iTunes Match. To reset a library in the cloud, so you have to tweak: if you do not already have one, you will have to create a library that will contain only pieces in the cloud. To do this, quit iTunes, and then run it by pressing the ⌥. Then choose to create a new library.
Connect to iTunes Match (iTunes Store> iTunes Match) and wait until your entire library in the cloud appears. You might be tempted to select all and delete everything at once: it would be a mistake. Relations department to developers Apple has confirmed that to immediately delete songs from iTunes Match, it was not to remove more than 1000 pieces at a time. In short, delete 999 songs by 999 until you have deleted all your songs to iCloud.
Prior to removal, make sure you have kept a copy of all your songs in the cloud. Update your iTunes library Match (Store> Update iTunes Match): it is now empty and de facto reset on Apple's servers. Quit iTunes and restart holding down ⌥ and select your usual library containing your songs locally. Connect to iTunes Match: since your library in the cloud is empty, the longest stage of synchronization will start from scratch.