What happened:
The editor occasionally crashes (aprox 20% of the time) with a directx11 access violation error when setting up an external texture. We're using a plugin to create a separate Directx9 context for doing video rendering and then exporting the texture handle to Unity's directx11 context in a Unity rendering plugin, then using that handle with Texture2D.CreateExternalTexture().

How we can reproduce it using the example you attached:
Open scene "test" and press Play. Video should appear on the falling plane after a half second. After video appears, press "R" key to reload the scene. Repeat this process until editor crashes when the video would appear, usually <10 tries.