Issues Accessing bookContent Properties in UXP Plugin for InDesign

i'm migrating an old Indesign script i created to process book documents before starting to work on them.
i'm trying to get a list of all documents in the book and open each one, process and save it.
i created a UXP plugin, but when i'm trying to access the bookContent properties like the filePath i'm getting back rejected promisses and not valid objects
i already tried adding full file system permissions with no luck.
i tried

await book.bookContents.firstItem().fullName

but i'm getting back some kind of Symbol()
without await i get a resolved Promise which the result is an "n"...

<Title renamed by MOD>