Cosmic miscalculite
An intelligent person who is capable of doing math but, for reasons of entropy/fate/providence/bad luck, gets the answers wrong anyway, even to the extent that even math teachers are stumped as to why.
"I checked my answer 20 times. 20 TIMES! And the teacher checked it five times! I showed my work twice over. Neither of us knows how I got question 4 so wrong."
"You poor cosmic miscalculite..."
"You poor cosmic miscalculite..."