Assuming you are in a region where you are allowed to redownload your past music purchases, the normal solution is to delete the problem tracks from your iTunes library, close and then reopen iTunes, go to the iTunes Store home page, click the Purchased link from the Quick Links section in the right-hand column, then select Music and Not on this computer. You should find download links for your tracks there.
While downloading select Downloads in the left-hand column and make sure Allow Simultaneous Downloads is unticked.
If the problem persists, or that facility is not yet available in your region, or you are concerned that tracks in question are no longer available in the store then contact the iTunes Store support staff through the "Report a problem" links in your account history, or via Contact Support.
See also:
HT5085 - iTunes in the Cloud and iTunes Match Availability
HT2519 - Downloading past purchases from the App Store, iBookstore, and iTunes Store
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