Hi, thanks for sharing this problem.
I have no experience with this particular package and we haven't done any work to verify it can work with NCrunch. However, there may be a couple of options available to you.
The first option is to try including the referenced files in your NCrunch workspace by adding them to the 'Additional files to include' NCrunch setting. Most likely they aren't being flagged up by MSBuild, so NCrunch doesn't know to copy them to the workspace. By including them like this, they should be in the workspace NCrunch uses for building and it may allow your build to pass as normal.
The second option is to find a way to disable the react build step in your project. This could by done by adding a condition to a build target or adding a conditional property to your build. This might require you to run through the relevant target files to see how you can disable them in the NCrunch build.
This documentation page gives an example of how you can add conditional behaviour to your build system so that it behaves differently under NCrunch.
