Hiho!
Later in the game, a new type of fast moving UFO with distinctive twin engines appears . I made a screenshot to clarify which one I'm talking about. You'll find it attached to this posting.
If I manage to shoot this ship down, there is a ground mission.
I send my transporter there and the dialogue "Enter" "Cancel" appears. I can't select "Auto Mission".
If I click "Enter", there is a very brief delay as if the game tried to do/load something and then I'm back at the geoscape and the transporter is still hovering above the target. Trying again won't change anything.
I can continue the game normally but I can't enter missions of this type. So it's not a grave thing.
Just wanted to let you know.
Andy