It suffers the usual problems of tests, among which are that test-taking is itself a skill.

That said, I don't think re-taking the test produces a valid result - a lot of the time I spent on the test was figuring out the rules of the puzzles as much as solving them. The problematic nature of the initial result is a reflection of the weakness of the test, as you noted, but re-taking the test simply introduces a new suite of problems.