Dual Extruders and move axis operation

I am building my 3rd custom 3D printer, but this is the first one I've done with dual extruders. I got the printer powered up and running for the first time last night, but I have some questions on the behavior of the two extruders and wanted to clarify.

General Info:

I am using a MKS Gen 1.4 Board with DVR8825 stepper drivers.
Not that it matters, but I've got two e3D titan extruders mounted in a Bowden configuration.
I have an endstop setup as a filament runout sensor, I only have one configured at the moment, not two.

When I was going through last night and testing all the axis movements and functionality through the LCD interface, I noticed some odd behavior with the extruders when trying to move them using the "Move Axis" menu.

I have 3 menu options under "Move Axis" relative to the extruders:

Extruder
Extruder 1
Extruder 2

I heated both hot ends up to 200F to ensure I wouldn't run into issues triggering the low temp extrusion. I made sure both were at temp before attempting the test.

If I select Extruder 1 and manually move it, it works just fine. Display shows the distance I've moved as normal.
If I select Extruder 2 I will see the distance that I already moved Extruder 1 displayed on the screen before I start any further movements. I turn the knob and I don't get any movement out of Extruder 2, but the number on the screen changes as I turn the dial as if it were moving. I also don't think I was getting any movmement from Extruder 1.The same thing happens if I start trying to move extruder 2 first, but it starts off at zero.
Finally, if I just try moving Extruder, I think extruder 1 is the one that moves.

I suspect it's behaving like both extruders are acting as one. The fact that the value of extruded length carries over no matter what menu option I choose is leading me to think that. I want to make sure my firmware is configured properly before I start chasing hardware issues.

Now, I'll say that it's possible I have a bad stepper driver. The batch of drivers I ordered had one bad driver in it already that I found on my other custom printer. The driver that was connected to extruder 2 (E1 position on the board) was much hotter than the others when I felt it, and it was set to the same voltage as the others.

I'm using Marlin 1.1.9 with a RepRapDiscount FULL GRAPHIC Smart Controller. I've pasted the first portion of my configuration.h file below through the section on extruders. I don't know if there is somewhere else within the firmware I have to go to adjust the menu functionality, or if it should already be setup to support driving the extruders individually rather than as a combo.

#include 

/**
 * Marlin 3D Printer Firmware
 * Copyright (C) 2016 MarlinFirmware [https://github.com/MarlinFirmware/Marlin]
 *
 * Based on Sprinter and grbl.
 * Copyright (C) 2011 Camiel Gubbels / Erik van der Zalm
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see [www.gnu.org].
 *
 */

/**
 * Configuration.h
 *
 * Basic settings such as:
 *
 * - Type of electronics
 * - Type of temperature sensor
 * - Printer geometry
 * - Endstop configuration
 * - LCD controller
 * - Extra features
 *
 * Advanced settings can be found in Configuration_adv.h
 *
 */
#ifndef CONFIGURATION_H
#define CONFIGURATION_H
#define CONFIGURATION_H_VERSION 010109

//===========================================================================
//============================= Getting Started =============================
//===========================================================================

/**
 * Here are some standard links for getting your machine calibrated:
 *
 * [reprap.org]
 * [youtu.be]
 * [calculator.josefprusa.cz]
 * [reprap.org]
 * [www.thingiverse.com]
 * [sites.google.com]
 * [www.thingiverse.com]
 */

//===========================================================================
//============================= DELTA Printer ===============================
//===========================================================================
// For a Delta printer start with one of the configuration files in the
// example_configurations/delta directory and customize for your machine.
//

//===========================================================================
//============================= SCARA Printer ===============================
//===========================================================================
// For a SCARA printer start with the configuration files in
// example_configurations/SCARA and customize for your machine.
//

//===========================================================================
//============================= HANGPRINTER =================================
//===========================================================================
// For a Hangprinter start with the configuration file in the
// example_configurations/hangprinter directory and customize for your machine.
//

// @section info

// User-specified version info of this build to display in [Pronterface, etc] terminal window during
// startup. Implementation of an idea by Prof Braino to inform user that any changes made to this
// build by the user have been successfully uploaded into firmware.
#define STRING_CONFIG_H_AUTHOR "(none, default config)" // Who made the changes.
#define SHOW_BOOTSCREEN
#define STRING_SPLASH_LINE1 SHORT_BUILD_VERSION // will be shown during bootup in line 1
#define STRING_SPLASH_LINE2 WEBSITE_URL         // will be shown during bootup in line 2

/**
 * *** VENDORS PLEASE READ ***
 *
 * Marlin allows you to add a custom boot image for Graphical LCDs.
 * With this option Marlin will first show your custom screen followed
 * by the standard Marlin logo with version number and web URL.
 *
 * We encourage you to take advantage of this new feature and we also
 * respectfully request that you retain the unmodified Marlin boot screen.
 */

// Enable to show the bitmap in Marlin/_Bootscreen.h on startup.
//#define SHOW_CUSTOM_BOOTSCREEN

// Enable to show the bitmap in Marlin/_Statusscreen.h on the status screen.
//#define CUSTOM_STATUS_SCREEN_IMAGE

// @section machine

/**
 * Select the serial port on the board to use for communication with the host.
 * This allows the connection of wireless adapters (for instance) to non-default port pins.
 * Serial port 0 is always used by the Arduino bootloader regardless of this setting.
 *
 * :[0, 1, 2, 3, 4, 5, 6, 7]
 */
#define SERIAL_PORT 0

/**
 * This setting determines the communication speed of the printer.
 *
 * 250000 works in most cases, but you might try a lower speed if
 * you commonly experience drop-outs during host printing.
 * You may try up to 1000000 to speed up SD file transfer.
 *
 * :[2400, 9600, 19200, 38400, 57600, 115200, 250000, 500000, 1000000]
 */
#define BAUDRATE 250000

// Enable the Bluetooth serial interface on AT90USB devices
//#define BLUETOOTH

// The following define selects which electronics board you have.
// Please choose the name from boards.h that matches your setup
#ifndef MOTHERBOARD
  #define MOTHERBOARD BOARD_MKS_GEN_13
#endif

// Optional custom name for your RepStrap or other custom machine
// Displayed in the LCD "Ready" message
#define CUSTOM_MACHINE_NAME "Box Printer"

// Define this to set a unique identifier for this printer, (Used by some programs to differentiate between machines)
// You can use an online service to generate a random UUID. (eg [www.uuidgenerator.net])
//#define MACHINE_UUID "00000000-0000-0000-0000-000000000000"

// @section extruder

// This defines the number of extruders
// :[1, 2, 3, 4, 5]
#define EXTRUDERS 2

// Generally expected filament diameter (1.75, 2.85, 3.0, ...). Used for Volumetric, Filament Width Sensor, etc.
#define DEFAULT_NOMINAL_FILAMENT_DIA 1.75

// For Cyclops or any "multi-extruder" that shares a single nozzle.
//#define SINGLENOZZLE

/**
 * Průša MK2 Single Nozzle Multi-Material Multiplexer, and variants.
 *
 * This device allows one stepper driver on a control board to drive
 * two to eight stepper motors, one at a time, in a manner suitable
 * for extruders.
 *
 * This option only allows the multiplexer to switch on tool-change.
 * Additional options to configure custom E moves are pending.
 */
//#define MK2_MULTIPLEXER
#if ENABLED(MK2_MULTIPLEXER)
  // Override the default DIO selector pins here, if needed.
  // Some pins files may provide defaults for these pins.
  //#define E_MUX0_PIN 40  // Always Required
  //#define E_MUX1_PIN 42  // Needed for 3 to 8 steppers
  //#define E_MUX2_PIN 44  // Needed for 5 to 8 steppers
#endif

// A dual extruder that uses a single stepper motor
//#define SWITCHING_EXTRUDER
#if ENABLED(SWITCHING_EXTRUDER)
  #define SWITCHING_EXTRUDER_SERVO_NR 0
  #define SWITCHING_EXTRUDER_SERVO_ANGLES { 0, 90 } // Angles for E0, E1[, E2, E3]
  #if EXTRUDERS > 3
    #define SWITCHING_EXTRUDER_E23_SERVO_NR 1
  #endif
#endif

// A dual-nozzle that uses a servomotor to raise/lower one of the nozzles
//#define SWITCHING_NOZZLE
#if ENABLED(SWITCHING_NOZZLE)
  #define SWITCHING_NOZZLE_SERVO_NR 0
  #define SWITCHING_NOZZLE_SERVO_ANGLES { 0, 90 }   // Angles for E0, E1
  //#define HOTEND_OFFSET_Z { 0.0, 0.0 }
#endif

/**
 * Two separate X-carriages with extruders that connect to a moving part
 * via a magnetic docking mechanism. Requires SOL1_PIN and SOL2_PIN.
 */
//#define PARKING_EXTRUDER
#if ENABLED(PARKING_EXTRUDER)
  #define PARKING_EXTRUDER_SOLENOIDS_INVERT           // If enabled, the solenoid is NOT magnetized with applied voltage
  #define PARKING_EXTRUDER_SOLENOIDS_PINS_ACTIVE LOW  // LOW or HIGH pin signal energizes the coil
  #define PARKING_EXTRUDER_SOLENOIDS_DELAY 250        // Delay (ms) for magnetic field. No delay if 0 or not defined.
  #define PARKING_EXTRUDER_PARKING_X { -78, 184 }     // X positions for parking the extruders
  #define PARKING_EXTRUDER_GRAB_DISTANCE 1            // mm to move beyond the parking point to grab the extruder
  #define PARKING_EXTRUDER_SECURITY_RAISE 5           // Z-raise before parking
  #define HOTEND_OFFSET_Z { 0.0, 1.3 }                // Z-offsets of the two hotends. The first must be 0.
#endif

/**
 * "Mixing Extruder"
 *   - Adds G-codes M163 and M164 to set and "commit" the current mix factors.
 *   - Extends the stepping routines to move multiple steppers in proportion to the mix.
 *   - Optional support for Repetier Firmware's 'M164 S' supporting virtual tools.
 *   - This implementation supports up to two mixing extruders.
 *   - Enable DIRECT_MIXING_IN_G1 for M165 and mixing in G1 (from Pia Taubert's reference implementation).
 */
//#define MIXING_EXTRUDER
#if ENABLED(MIXING_EXTRUDER)
  #define MIXING_STEPPERS 2        // Number of steppers in your mixing extruder
  #define MIXING_VIRTUAL_TOOLS 16  // Use the Virtual Tool method with M163 and M164
  //#define DIRECT_MIXING_IN_G1    // Allow ABCDHI mix factors in G1 movement commands
#endif

// Offset of the extruders (uncomment if using more than one and relying on firmware to position when changing).
// The offset has to be X=0, Y=0 for the extruder 0 hotend (default extruder).
// For the other hotends it is their distance from the extruder 0 hotend.
#define HOTEND_OFFSET_X {0.0, 40.00} // (in mm) for each extruder, offset of the hotend on the X axis
#define HOTEND_OFFSET_Y {0.0, 0.00}  // (in mm) for each extruder, offset of the hotend on the Y axis

Just to close this out. I discovered my problem was a bad cable to the stepper motor from the driver. Swapping to a different cable resolved the issue. It is still strange that a resistance check between the start and end pins on the connector for each strand showed no open lines, but apparently the cable was still faulty.