Go to your Library window, select incomplete folder, press Explore button. Then the folder will open for you. Now arrange it by date modified. This will list files changed most recently at the top. Now see if there's 2 videos listed that are the same. One may have a different or slightly different name. This has been a characteristic of LW for a long time. Sometimes because there's a bit or byte different, LW decides it was not the file you were after & finds a different source for the file or else, the original one was changed .. perhaps that person changed its description ... I am not sure.

Other than that, if you didn't close LW properly before shutting down computer, your download prefs will have been corrupted. Meaning it will have gone to zero. But normally if that happens your incomplete downloads will refuse to load into the download window & you will receive an error message. But all the same should with the recent versions of LW start from where it left off if it is resumed from the library.