When 50% FIB retracement does not hold true for a long or short

With my 3 strong candle displacement theory to the upside or downside leaving a fair value gap.
I have noticed that if there is a strong reaction to the 50th percentile retracement with continuation to the up or downside, this is a confirmation that this may hold through.
But if there is a deep dive below the 50% retracement, it tells me in most cases that we should expect a reversal.