I’m beginning to think Incapacitation is not random, but fixed. I’ve been recording missions done and Fatigue Percents and in 81 missions done, ranging up to 50% Fatigue on mission completion, only 1 mission caused Incapacitation. That was the one time my Fatigue would have hit 50.xx%. All other missions, even ending with 49% Fatigue have not caused an Incapacitation. I will also note, in earlier tests, I have managed to see 50% that caused no Incapacitation, so it would seem that some part in the decimal value is the threshold.
More data is needed to really be sure I just haven’t been very lucky, so time will tell if this holds.