I hate to be a bother, but could the latest NPM packages be missing grid texture?
I followed the example for setting up a new ES6 project but even with all of the additional packages downloaded the grid texture import fails as not found. I also don’t see grid texture anywhere in any of the packages, core / material / or otherwise.
adding @sebavan
I have an ES6 project using version 4.2.0-beta.1 from NPM and the grid material is present and working for me.
Yeah, I just figured it out. It was of course nothing more than an ID 10 T error on my part 
Been offline for surgery for months and I seem to have forgotten everything basic.
All is well.
No problem better to check twice than creating in an issue in the release