I'm using a MacBook Air with the last update (Mac OS High Sierra, version 10.13.2) and I'm experiencing problems with the drag and drop function. I've always done it with no problem, but since I updated to the last version I seem to be unable to do it: I can mark the item to drag with no difficulty, but when I go to the other location to drop it (I tried it with different locations), it says it's dragging it, making the usual sound, but eventually says it's unable to drop the item. I repeat: the error message doesn't say that the item is no longer visible, but that the release was unsuccessful.
(sorry if I don't write the exact words: I'm using the laptop in Italian. But you know what I mean!).