Inventory - Items: Exports do not include serials numbers or batch numbers (even not when I chose "Include Serial Numbers") ?

Inventory - Items: Exports do not include serials numbers or batch numbers (even not when I chose "Include Serial Numbers") ?

When I export items (by showing all active items, and selecting "Export Items" in the hamburger-menu), I can chose the export to include Batch Numbers and/or Serial Numbers.

But the field "Serial Numbers" in both the CSV-file or XLSX-file is always empty, even though I have items that have Serial Numbers associated with them. 
Also the Backup of Inventory (or Books) does not contains any files with Serial Numbers. 

(The only way to export Serial Numbers, seem to select an individual Item, go to the Serial Numbers-tab, and select Export on that page.)