Command line build failing but works great when run from the editor.

I'm working on setting up automated builds for a Unity 5 project and I've made some progress building within Unity but now that I'm moving on to building from the command line I'm running into a snag and hopeful I can get some help.

To start I've made a static class and added some menu items to Unity for single-click builds. Some sample code:

 using UnityEngine;
 using UnityEditor;
 
 namespace Builds
 {
     public static class AutomatedBuilds
     {
         private static string _buildPath = "mypath";
         private static string _appName = "myapp";
         private static string _buildNumber = "0.0.0";

         [MenuItem("Build Tools/Windows x64 Debug", false, 0)]
         public static void BuildWindows_x64_Debug()
         {
             BuildPipeline.BuildPlayer(
                 _levels,
                 string.Format("{0}/{1}/{2}_{3}_{4}.exe", _buildPath, "win", _appName, "Debug", _buildNumber),
                 BuildTarget.StandaloneWindows64,
                 BuildOptions.AllowDebugging
             );
         }
     }
 }
 

After this script gets compiled by Unity I get a menu item called "Build Tools" with a command called "Windows x64 Debug". Clicking this invokes the build and it all works great: my build gets made and I can run it no problem.

My next step is to run this all from the command line. The command I'm running looks like:

 '"C:\\Program Files\\Unity\\Editor\\Unity.exe" -projectPath E:\path\to\UnityProject -batchMode -executeMethod AutomatedBuilds.BuildWindows_x64_Debug -logFile E:\path\to\BuildLog\build.log -nographics -quit'

This also runs but I get the following output in the console:

 Aborting batchmode due to failure:
 Scripts have compiler errors.

Since that's a vague error message I've checked the build.log file generated with the command and there is a ton of stuff in there but it all looks like general build stuff except for this bit toward the end:

 -----CompilerOutput:-stderr----------
 
 Assets/Scripts/Test/TestUI.cs(17,27): error CS0234: The type or namespace name `Dropdown' does not exist in the namespace `UnityEngine.UI'. Are you missing an assembly reference?

The file in question looks like:

 using UnityEngine;
 using UnityEngine.UI;
 using UnityEngine.Assertions;

 using GameEvents;
 using DataContracts;

 public class TestUI : MonoBehaviour {

     public InputField[] SetCardFields;
     public GameObject TestPanel;

     public GameObject DeckView;
     public GameObject TestCardPrefab;

     [Header("Charm Setter")]
     public Dropdown CharmSelectionDropdown; // <-- THIS IS THE LINE CALLED OUT IN THE LOG

     // more but you get the idea

I've confirmed that Dropdown is a Unity UI class so it should be good (also it compiles when running Unity).

I'm running Unity 5.2.2f1 64 bits on Windows 10 x64. I have a similar script (though the project doesn't currently use Unity UI) that builds a different project without issues from the command line.

Ideally I need to stick with 5.2.2f1 as I'm working with a team and cannot just upgrade on a whim. If this is a known bug in 5.2.2f1 then an upgrade is probably called for but a Google search reveals nothing.

So, my question: why does Unity crash when building from the command line but not from within the Unity application itself? What are steps can I take to get to the bottom of this?