I would start with an informal inquiry as to how it is possible to fail if you were comparable in both categories given that the comparable range is between 75-80. They may have a reasonable response. Here is what I am thinking (this is going to be tough to explain in writing but I'll try):
You were comparable on MCQ to the people who got between 75-80 OVERALL on the exam. However, in theory, a lot of those people could have been stronger than you on SIMS. So let's say that Person A scored a 76 OVERALL on the exam. You were comparable to Person A on the multiple choice. However, Person A scored STRONGER on the SIMS. So perhaps Person A, to whom you were comparable, could have scored like 72 or 73 on the MCQ part and maybe 78 or 79 on the sims.
On the flip side, you were comparable to person B on the SIMS section. However, maybe that person got like 73 on the SIMS and was STRONGER on the MCQ, scoring like a 78 or 79. Even though you were comparable to that person on the SIMS, he actually did better than you did on the MCQ.
Where it gets tricky, is what happens when you blend all of those scenarios together (Person A and Person B). Is it possible that you were comparable to Person A on the MCQ, thereby getting a 74, and comparable to Person B on the SIMS, thereby getting a 74? In theory, perhaps you could have been comparable to both of their weaker areas without a compensating STRONGER area to put you over the hump.
Am I crazy?