 The probability distribution for the result of such a  Stern-Gerlach experiment  can be conveniently expressed in terms of the quantum mechanical spin operators—for a spin-1/2 particle given by certain 2 by 2 matrices called the Pauli spin matrices—in the manner alluded to  above.  From a Bohmian perspective there is no hint of paradox in any of this—unless we assume that the spin operators correspond to genuine properties of the particles.