[gianni_fed]

I made a backup of my library and, to my amazement, Caliber has not copied a large number of books giving me this error: ValueError: Not a ZIP file.
In my experience, the ZIP format is not absolutely reliable, over the years I lost many files because I had zipped them, what I know is that if you do not put the "recovery record" when you compress a file and a "corrupt header" occurs in the zipped file, the latter is unrecoverable.
From the analysis of the corrupt epubs, as can be seen in the enclosed images, the recovery record is absent, why?
What do you know, is there a way to recover them?
Thanks and bye,
Gianni
PS. sorry, I found also another error:
File "site-packages\calibre\ebooks\metadata\epub.py", line 165, in get_zip_reader
File "site-packages\calibre\ebooks\metadata\epub.py", line 148, in __init__
File "site-packages\calibre\ebooks\metadata\epub.py", line 98, in __init__
File "site-packages\calibre\ebooks\metadata\epub.py", line 153, in open
File "site-packages\calibre\utils\zipfile.py", line 995, in read
File "site-packages\calibre\utils\zipfile.py", line 1030, in open
BadZipfile: Bad magic number for file header