Course not launching when accesed via the company firewall (Pulse Secure Juniper)

We are encountering a problem with Storyline courses hosted in Moodle. They work fine when accessing via the intranet but when opening from outside they give an error.

We think that it is due to the change in URL that the secure interface causes. See the screenshot with the URL and the error in app.min.js. It is in the SlicedtoArray function. If removed the course launches but after navigating a few screens it closes.

Any ideas? can it be due to the URL and parsing of parameters?

Thanks