BUG: Add Node doesn't accept more then n-instructions? Black Shader when re-opening Unity!

I've crated a shader that utilizes multiple nodes that get combined together using 'Add'.

For example: a Color Node and Texture2D Node get combined using a Multiply Node, that Multiply Node gets added to the Add Node. I repeat this process 4 times to create a 'masked color picker' and assign directly to the Diffuse Slot. However, when I add my 4th set to the Add Node and close out of Unity and open it back up, the shader is black until I compile it again. When I only have 3 sets assigned to the Add Node, it works fine. As soon as I add that 4th set and close out of Unity, I get a black shader upon re-opening.

When I deploy to iOS with 4 sets added, the shader is also black, even after compiling. However, it works will 3 sets added.

Not sure what is going on.