One Slot has already a packed cargo, another one is put on flatbed with the crane. The only available menu option is to unpack cargo. THEN you can pack/fix both. I do expect a "pack cargo" option as long as there is "unpacked" cargo available.
Translation with Crane:
- English: Activate Anchor, perfect.
- German: "Haken aktivieren" literally means "activate hook". "Stützen betätigen" would be the much better description to toggle the "Anchors".