I cloned your app and ran it as described, and I reproduced the problem.
I deleted the DataGridJson component from the app, added my DataGridJson as dependency and ran it, and it worked as expected.
I tried to do a quick diff between my version and yours, but it was too difficult, because the folder structure changes. So I don’t know what went wrong.
I would suggest for you to clone the DataGridJson app to your account and use it as a dependency on the new app. This would avoid any conflict with anything outside the modules, like javascript or other resources.