Ruby on Rails 3. How to overcome problems with JavaScript on Production?

Question

JavaScript

There is a RoR application that is deployed on Heroku, and in two instances.
A - apply.arkavis.com
B - enigmatic-meadow-5839.herokuapp.com
The applications are absolutely identical, with the exception of some settings that do not affect the problem in any way.
The problem is that when accessing A, an error occurs js-agent.newrelic.com/nr-248.min.js not found (please see the console), but on B such an error does not occur. Tried in all browsers (Ubuntu 13.10).
On my brother's PC (Ubuntu 13.10), on the contrary, it occurs on B, on A, no. And then only in Chrome, in Firefox for both applications everything is ok.
Tell me what could be the matter and in which direction to "dig"?

Answer 1

B in general lies with an error
A everything is fine, but by mistake it was a newrelic problem, apparently the domain is linked there