Hi Denver,
If I understand correctly the scenario you're describing (and I'm a little tired right now, so I may not be
), I think the reader is deciding that the book records that have been updated to appear on the Book list by the Book List plugin have changed and it reprocesses them, which ends up resetting the author metadata, overriding what you want that data to appear as.
I see this with new books added to the reader quite often (and I'm not sure why it happens as the plugin synchronizes the date in the metadata cache file to align with the book file timestamp, which should trick the Sony firmware into thinking the records have not changed).
In any case, when this occurs, connecting the reader again to your computer and letting Calibre do its thing (without invoking the plugin action) should put things back in order. Have you tried that?