Yeah, I just spent some time trying to figure this out after seeing your post. I have not noticed a flaw described in this way on nearly any other test that I can think of, and I've been through a few of them. I believe your characterization of the …
A-->B-->C-->D
Whatever variable is negated after your original chain is established, start at that point and run it backwards (right to left), negating as you go. Ignore everything to the right of the negated variable.
If C is negated, th…