There has been an issue with Windows Defender ransom ware protection and LibreOffice at least since 2016:
If you try to save and open files from at least a non-standard document folder, e.g. Desktop, Defender will block that particular process because it thinks something malicious is going on. The alert is not prompted directly, but silently hidden in notification center.
For a non-technical user this behavior is nontransparent, so they blame LibreOffice being faulty.
Well done, Microsoft.
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