Dealers hedging short options near the money must buy as price falls and sell as it rises. That mechanical flow damps moves around the strike with the largest open-interest, and price can grind sideways into the close.
Pinning is a tendency, not a law. Real news overwhelms it instantly, and it is much weaker in names where the options market is small relative to share volume.
Example: XYZ has 45,000 contracts of open interest at the $50 strike and fewer than 3,000 at any other. Friday's range is $49.80 to $50.30 on heavy volume, and the close is $50.02. The following Monday, with hedges gone, XYZ opens at $51.10.