Just added three zippy links, the message appeared again
all three download links marked as duplicate:
One of the files has a combination of numbers and letters (as it often is) instead of file.html.
I added three more zippy downloads without a problem. Not being marked as duplicates. All of their file names were a combination of numbers and letters, without extension.
Unfortunately I cannot find script_errors.txt file, may be there is not one created after to log that error?
But, it seems (like it was yesterday) or may be the error only appears once in a JD session (from start to close of JD) and never again in the sesson, so one could leave it as it is.