Juniper Networks Browser VPN - Problem in Firefox only

[nelfer]

Hi,
We have a customer that is using Juniper Networks Browser VPN, which is basically like a proxy "web server" that redirects internally to the web server we want to access. In order to do this, their system overrides (on the fly I suppose) any link or AJAX calls to the new URL that will handle it. Example:

Real URL: www.example.com/abc
Juniper VPN URL: secure.example.com
Converted URL (what the browser finally shows to user): secure.example.com/,danainfo=www.example.com/abc

So everything works fine, except when using some pages that use Vue and Vue-Resource and only in Firefox.
Technically no error is displayed, but it seems like $http.get never executes. Debugging it goes into a lot of functions (form veu-resources and juniper inserted functions) and at the end, no promise is resolved (so it's not like the promise gets rejected). And in the Network panel there's no connection happening.

This works fine in Internet Explorer and Chrome. So not really sure what's going on in Firefox.

So why do I come here to you? Because we have other pages that use other libraries for doing AJAX requests and those do not fail (in any browser). So, something, somewhere inside vue-resource, causes it not to work (only on Firefox and only when using that VPN)

Any help on how to debug this will be appreciated.
Thanks

P.S. By accident I noticed that firefox does not allow to add headers to a request before the connection is open. Other browsers do. So I wonder if there's some code when the connection is being open and maybe the VPN is trying to add some headers before it gets opened.