Is there a reason why this is happening? "Run Code" returns the expected result, but it's all wrong when submitted.....
Nevermind, I was reading an array over the boundary. Must be so that, when running the test by itself, the byte past the array boundary happens to be "0" (i.e. false), while running previous tests sets it to some value, somehow, which triggers an incorrect behaviour.
I still love you, C.