What happened?
If you connect a node in a path of nodes leading to any master node input besides position, and then try to connect that node to a path of nodes leading to position, the "bubble" of the inputs to those nodes will close and you won't be able to connect it. The reverse is also true (nodes connected to paths leading to position can't be connected to paths leading to anything else).

Steps to reproduce:
1. Open NodeConnectionTest.shadergraph
2. Try to connect the Out(1) output of the Simple Noise node to the B(3) input of the Multiply node. (see ShaderGraphNodeConnectionBug01.gif)

Expected result: you should be able to connect this output with this input.
Actual result: The input bubble "closes" and you can not connect the output to the input.

Workaround: If you create a "Vector 1", "Vector 2", "Vector 3", or "Vector 4" node, you can plug the desired output or outputs into the input or inputs of the Vector node, and the output of the Vector node into the input of the desired node (see ShaderGraphNodeConnectionBugWorkAround01.gif). This should not be necessary for the user to do, and the user can not be expected to figure out this work around. Additionally, the fact that this workaround works, and results in expected behavior, means that there is no functional reason for nodes to not be able to connect to paths leading to both "position" and other master node inputs at once.

Concern: Make sure that, after this is fixed, nodes that have code that should not be able to run in the vertex shader (such as Sample Texture2D) are still not able to route into the "position" node. If they are able to do so, it might cause a crash or cause the shadergraph to not compile.