Cargo drones unavailabe at player shipyard

[letsplay]

Cannot select cargo drones for large transporter and large miners in player shipyards, neither when specifying build nor upgrade/repair.
Have drones blueprint; and other drones are available in both build and upgrade/repair. Cargo drones do not appear as an option in the relevant menu.

(Repeat of post in 'general forum' as someone suggested better to raise issue here.).