I just turned off all generation of ORIGINAL_EPUB, and deleted all ORIGINAL_EPUB from my library. If I ever need to go back to the original copy, I'll redownload it from whence it came. Typically, the original is sitting in my Downloads folder when I do my initial edits, so it's easy to reimport.
There's a minimal risk that the item in question will no longer be available, but I'll take that risk.
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