I did zip the downloaded contents to a file locally, with no error. I am assuming something to do with a max master zip size.
There are limits to the size of repos, the size of individual files etc.
This is one reason I have never created an actual GitHub release. If I did just 3 versions it would be almost 15GB. I need to conserve that space until I finish this. I have no way of knowing how large this will end up being.