1. The Fed now pays attention to it, so its indicator value could be dramatically weakened, or erased. (Previous Feds continued to raise rates after an inversion before previous recessions, while this Fed has done the opposite lowered them.)
or...
2. Inversions become a self-fulfilling prophecy. Despite low inflation, low unemployment, and healthy profit growth, markets decline due to the assumption that the yield curve inversion is a perfect forward indicator of recession.