UPhysicsConstraintComponent SetPositionTarget doesnt work

It seems that when calling SetLinearVelocityTarget() works on Runtime, but for some reason the function SetLinearPositionTarget doesnt work when changed. Why is that? Whats the procedure to be able to change the Position Target so that a joint changes of position based on for example a key press or something in runtime?

For example , this doesnt work, but I dont know why, because when setting a position through the BP it moves to that position, but changing in runntime seems to not work? Is it buggy?

UPhysicsConstraintComponent* ConstraintComp = nullptr;
// This function updates the ConstrainComp with the value of the BP joint
UpdateConstraintComp_from_BluePrint();

float yaw;

    if (KeyNum1Pressed==1.0 && KeyNum2Pressed==0.0)
    {
        yaw = 90.0;
        FVector TargetOrientationFVector = FVector(yaw,0.0,0.0);
        UE_LOG(LogTemp, Warning, TEXT("yaw = %s"),*FString::SanitizeFloat(yaw));
        ConstraintComp->SetLinearPositionTarget(TargetOrientationFVector);

    }else if(KeyNum1Pressed==0.0 && KeyNum2Pressed==1.0)
    {
        yaw = -90.0;
        FVector TargetOrientationFVector = FVector(yaw,0.0,0.0);
        UE_LOG(LogTemp, Warning, TEXT("yaw = %s"),*FString::SanitizeFloat(yaw));
        ConstraintComp->SetLinearPositionTarget(TargetOrientationFVector);

    }else
    {
        yaw = 0.0;
    }

Has anybody used this and made it work?