Can't Build PC Standalone due to multiple namespace script errors but playable in editor

My project works fine when played in the Unity editor. However, when I try to build it for the PC, Mac, & Linux standalone, it fails to build and gives me multiple errors such as:

Assets/Scripts/Respawn.cs(4,19): error CS0234: The type or namespace name `SceneManagement' does not exist in the namespace `UnityEngine'. Are you missing an assembly reference?  

Assets/Scripts/CameraMovement.cs(5,31): error CS0246: The type or namespace name `MonoBehaviour' could not be found. Are you missing an assembly reference?  

Assets/Scripts/PlayerCharacter/HERO/HeroMovement.cs(40,16): error CS0246: The type or namespace name `Vector2' could not be found. Are you missing an assembly reference?  

and ends with

Error building Player because scripts had compiler errors

I have checked my scripts and none seem to be using the UnityEditor specific functions.
I am using Unity 5.6.1f1 Personal and there was a previous 4.6 installation when I updated to my current version (if that matters). I have also attempted a re-install of the current version by uninstalling and then re-installing the same version of Unity.

I have attached the editor log as well.

Any help would be greatly appreciated!

[96516-unitylog.txt|96516]

I might be wrong but I think this looks like the kind of error you get when the name of the script in the inspector does not match the name at the top in the actually code. did you try renaming any scripts recently?

For SceneManagement, you need to add “using UnityEngine.SceneManagement;” at the top of the script that’s using SceneManagement.

Could you post CameraMovement and HeroMovement scripts?