I don’t know when it occurs.
If you have NPC’s on, they give you missions. And if they die, the missions fail.
Maybe the old save file causes the problem.
I went back to 0.7.1-391.gda20884 . Then there are only two failed missions.
I have seen this before as well. It happens with a small number of npcs from static npcs with dynamic npcs off. Sometimes I will check my failed missions and there are so many failed “Find Antibiotics” that it lags out the game. The thing is, usually I have only 3 or 4 npcs alive at max and far more “Find Antibiotics” missions failed than is possible for them to give. It happens even if I never actually talk to the npc that gives that mission. I know they are pretty buggy atm though so I expect there to be some issues.