Npm 504 error on installing ionic 1.2

I have an app in production on ionic 1.2. In trying to deploy a new CI system, I found that our ionic dependency is broken. Has anyone else dealt with this?

I am not looking to upgrade ionic beyond 1.2 series. I have tried the latest 1.2.14 with the same result.

npm install ionic@1.2.13

from npm-debug.log

20316 http fetch 504 https://registry.npmjs.org/i/-/i-0.3.2.tgz
20317 info retry will retry, error on last attempt: Error: server error 504

This is apparently shrinkwrapped in ionic for “prompt”. I also opened a ticket. https://github.com/driftyco/ionic-cli/issues/1028