and this, kids, is why you check in your dependencies with your project. You can refer to them in your vendor folder for fun, no problem. BUT KEEP A LOCAL COPY IN YOUR REPO

This is for Composer, as wel as for NPM. You now introduced a third-party dependency into your development workflow. What will you do when github goes down for a week?

Seems to be luck of the draw whether each pageload goes through or not

Same here, couldn't update my packages with composer.