I have a simular problem,
I finished the third mission (the one with the whales), but when i land and end the mission correctly, i come to the heliport and see i have to do the mission over.
When i check the menus, and choose the career options, i see when i click the third mission the replay option.
Perhaps it has to to something with the update, i updated when i saved in the midst of the third mission. When i continued with the updated game, i couldn't select my save game, but when i slected revert mission, i could it play again from the start. So i did but when i finished then the mission, it seemed that i couldn't acces the fourth mission.