Missing movie files after moving iTunes library

I moved my iTunes library to an external hard drive. Music, tv programs & apps & most movies are working perfectly. Some movies that are appearing in my library are empty folders. when I click on the movies i get an error message saying they can not be located. I moved my itunes library several months ago and have only discovered this problem this week, I emptied my trash after checking that the itunes library was working.

I tried to re download my purchases using the following page:

HT2519: Downloading past purchases from the iTunes Store, App Store, and iBooks Store

Unfortunately, I can not find an icon to download the movies again - i have amended my itunes preferences. I have Itunes 11.1.3 on a Mac.

Any help would be very much appreciated.

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