Not only is it downloading the same .deb over and over even if it exists, it is downloading the wrong version. When the backports repo is available, t was downloading 2.0.3 from the main repo, the current version in backports is 2.1.2 that should be downloaded from backports.
The initial routine for the extra repos in debGetPkgList needed some cleaning up, it should be working now. Thanks for exposing the bug.
I placed the fix in the dCore.gz in the release_candidates section, please test.