In the Missile Design window, when I select a decoy that I designed (and researched), I receive this message
Moreover, if I select another missile before, and then the decoy, the values of the characteristics shown in the window don’t change, remain the ones of the missile.
But the decoys are listed in the developed missiles in the View Technology window.
The message doesn’t appear if I select a decoy that I salvaged from a NPR (and then researched).