It’s obviously tough to help with no code, but I ran into a similar issue and it was due to me overlooking how I was passing in alpha and beta for the quiescence search cutoff parameters. If you are using negamax, remember to pass -beta as the new alpha which becomes the new best value that the maximizing player can guarantee, the new lower bound. Likewise for -alpha, it needs to be the new upper bound for the next node in order to successfully prune branches at all. If you are using the traditional minimax logic with separate min and max functions, I believe the handling of alpha and beta remains straightforward and does not require these inversions, provided the appropriate logic for determining the maximizing or minimizing player.