I doubt it was 6-Br that caused the failure. I have seen lots of testing, and that's never occurred. If the wrong analysis is performed, andro can be a lab artifact, but only with high GC injection port temps. A reverse column LC at ambient temp is the only reliable test I've run across, and the analysis I would demand if accused of a false positive. Nevertheless, I think you're probably safe assuming the product had real 6-Br as the active.
As for WADA, they ban just about everything they can get away with, but I doubt DHAA will make the hot list anytime soon. It's just too ubiquitous.