Maybe there is something wrong with my computer. I installed a brand new instance of Calibre Portable, I created a "saved metadata" custom column. Updated FFF to use the new custom column. I made no other changes to FFF and downloaded two different stories.
One restricted:
https://archiveofourown.org/works/47189341
The other not restricted:
https://archiveofourown.org/works/34853359
In the saved metadata on the restricted I get all metadata except "Additional Tags" when I downloaded the not restricted fic, the "Additional tags" all appear in the tags column and in saved metadata column.
Amalthia