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Neuer Tag neuer Bug - Unable to list current working directory.
Pardon me for answering in English, but my German is very broken ...
I’ve experienced the same problem and found out that it’s caused (in my case) by the original product referencing a nonexistent product image in a nonexistent folder. When duplicating, the system tries to create a duplicate image file inside the nonexistent folder and this, of course, fails.