JS API 4.3 Custom Build Dojo Loader xhr Error

[Joel_Marshall]

I'm trying to make a custom build using the 4.3 JS API, but I keep getting a xhr build error (see below). I've never had this issue before with custom builds on the 3.x JS API. Is there something I need to add in the build.profile? I'm using the one recommended in the 4.x JS API Bower section guide from here: jsapi-resources/4.x/bower/dojo at master · Esri/jsapi-resources · GitHub.