It does make me more uncertain about most of the details. And that then makes me more pessimistic about the solution, because I expect that I’m missing some of the problems.
(Analogy: say I’m working on a math exercise sheet and I have some concrete reason to suspect my answer may be wrong; if I then realize I’m actually confused about the entire setup, I should be even more pessimistic about having gotten the correct answer).
Regarding your last point 3., why does this make you more pessimistic rather than just very uncertain about everything?
It does make me more uncertain about most of the details. And that then makes me more pessimistic about the solution, because I expect that I’m missing some of the problems.
(Analogy: say I’m working on a math exercise sheet and I have some concrete reason to suspect my answer may be wrong; if I then realize I’m actually confused about the entire setup, I should be even more pessimistic about having gotten the correct answer).