Cant rearrange Zotero items

I have items in collection A and want to move them to collection B.
I drag-dropped the items and to my surprize, they were copied, not moved. So now I have them in both A and B. I know, this is not a duplicate. I have removed them from A. But they did not remove from B.
If it is not a dupe, then how come I could delete one of them only ?
  • We went over this in depth in your other thread:
    http://forums.zotero.org/discussion/27095/duplicates-are-not-found-nor-can-i-rearrange-files/
    You didn't delete the item in collection A - as you say correctly you removed it from the collection, which means that it's still in collection B. If you had actually deleted the item - right-click-->delete selected item from Library - it would have been deleted from both collections.
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