1. I saved a game at the beginning of the turn.
2. I assigned a mission. (Mercury)
3. The mission failed. (Mercury catastrophic failure)
4. I loaded the savegame (see 1.), assigned the mission again and it failed again. (I tried it 10 or 15 times)
5. If I load the game (see 1.) and assign a other mission (e.g. Zond - Lunar flyby), this mission will fail.
6. Next season, I can assign the Mercury mission (see 2.) and that will be a success. = less prestige reduction and no dead astronaut

Looks like a possibility for cheating.