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Motion controls function in an odd way

tenchimod (1)
Hello all, I'm a newbie here. I haven't programmed in many years, and I wanted to make a very simple platform game. My other code works as intended, and I've included the relevant section below.

In the code I have so far, I use WASD to control movement, with Shift to make the sprite move faster on the X axis. Movement on the Y axis works as intended.

The problem is that the X axis will not work unless I first press A or D (for left or right) and then hold W or S. Once I hold A + W || S or D + W || S, the sprite moves. Shift works normally regardless.

In my debugging, I found that the boolean values are passed from handleMovement to the general update function. However, it only recognizes that the X axis values are passed if W or S is pressed as well. I'm quite frankly stumped, as this should be a fairly simple algorithm.

Any help would be greatly appreciated! 

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#include "Player.h"
#include "SDL.h"

Player::Player(const LoaderParams* pParams) : SDLGameObject(pParams){}

// draws the sprite
void Player::draw(){ SDLGameObject::draw(); }

// asks for the keyboard state, then updates the position
void Player::update(){
    handleInput();
        if(m_bMoveLeft){
        if(m_bRunning){
            m_velocity.m_x = -5;
        }
        else {
            m_velocity.m_x = -2;
        }
    } else if(m_bMoveRight){
        if(m_bRunning){
            m_velocity.m_x = 5;
        }
        else {
            m_velocity.m_x = 2;
        }
    } else if(m_bMoveUp){
        m_velocity.m_y = -5;
    } else if (m_bMoveDown){
        m_velocity.m_y = 5;
    }
    else {
        m_velocity.m_x = 0;
        m_velocity.m_y = 0;
    }
    handleMovement(m_velocity);
    m_currentFrame = 0;
    SDLGameObject::update();
}

// invokes the Vector class to calculate movement
void Player::handleMovement(Vector2D velocity){
    Vector2D newPos = m_position;
    newPos.m_x = m_position.m_x + m_velocity.m_x;
    newPos.m_y = m_position.m_y + m_velocity.m_y;
    m_position = newPos;
}

// dummy function, no use yet
void Player::clean(){}

// checks to see which button, if any, is held down
// it sets a movement flag to off or on
void Player::handleInput(){
    if(TheInputHandler::Instance()->isKeyDown(SDL_SCANCODE_D)){
        m_bMoveLeft = false;
        m_bMoveRight = true;
    } else if (TheInputHandler::Instance()->isKeyDown(SDL_SCANCODE_A)){
        m_bMoveRight = false;
        m_bMoveLeft = true;
    }
    if (TheInputHandler::Instance()->isKeyDown(SDL_SCANCODE_W)){
        m_bMoveUp = true;
        m_bMoveDown = false;
    } else if (TheInputHandler::Instance()->isKeyDown(SDL_SCANCODE_S)){
        m_bMoveUp = false;
        m_bMoveDown = true;
    }

    // default, sets all movement flags to OFF
    else {
        m_bMoveLeft = false;
        m_bMoveRight = false;
        m_bMoveUp = false;
        m_bMoveDown = false;
    }

    // checks to see if SHIFT is held down to run
    if(TheInputHandler::Instance()->isKeyDown(SDL_SCANCODE_LSHIFT)){
        m_bRunning = true;
    } else { m_bRunning = false; }
}
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