I think you should be very skeptical about possible errors in the OG 12. Let's not forget, these are retired questions - I do not think the GMAC could afford to use wrong questions in its testing. If this were ever proven, then indeed they'd have a problem and the test's credibility would be reduced.

I say post whatever issues you have in the appropriate section to get some feedback from the community - you'll sometimes notice that you've missed a crucial detail of some sort.