Clicking New field on /admin/settings/field/new hangs site
We discovered that the verbb/icon-picker plugin makes a call out to retrieve a file from it's cpresources cache and this was done with a fully qualified URL. Our AWS machines in CI/CD can be auto-provisioned and as such won't have their own name in the /etc/hosts file. So a call to https://fully.qualified.url/cpresources/577762fa/json/font-awesome.json?v=1556336828 was failing and hanging the site because it tried to get it five times in a row.

I've registered an issue with the Verbb folks, and put a PR together, so crossing my fingers!