Several subgraphs break when copied from one Unity Project into another. The error reported has to do with GUID.
This is a serious problem because it means collections of subgraphs can't be distributed as shareable libraries.

For instance from project

https://github.com/mmikk/Surfgrad-Framework-Unity-Shadergraph.git

Repro step:
1. Copy Assets\Subgraphs from this project into the new project.
2. Create a new shader graph.
3. Add the subgraph: Triplanar to surfgrad.

The project was made with unity 2019.3.0b4 and Package 7.1.7. They assets have to come from 7.1.7, otherwise this doesn't reproduce.
In this instance the new project was created on a different computer (still windows) and with 2019.3.0f5 but still Package 7.1.7.

Several of the subgraphs are breaking. An instance of Triplanar to surfgrad is just one example. Essentially any subgraph which uses other subgraph(s) in its graph breaks from what I can tell.

Note: Importing and exporting subgraph collections using .unitypackage file formats will maintain guid references between projects. Please use .unitypackage files to move subgraphs from one project to another until we can resolve this issue.