Considering the wide range of personality types needed in the Forces, I wouldn't discourage anybody who's determined to be part of the CF, only because they failed a test.
Studying in pedagogy, the very first thing we learn is that there are many intelligences. Not just 2 or 3, but 8, according to Howard E. Gardner. It is my opinion that all kinds of intelligence are useful to the Forces, in one trade or another. The thing is some of those intelligence types are very difficult to measure in a test. So, really, the fact the some have difficulties with the test while others thought it was a walk in the park means (for the most part) that the later possess an intelligence that is easier to test.