Engage opening in new window rather than within Salesforce

Hi,

At the end of last year, we launched Profiler & Engage with our sales team.

The tool is embedded into a Salesforce contact page and everything should work within the within the frame on the page - from checking the contact's activity through to choosing and sending a template. 

Everything has worked exactly as expected during testing, and still does now for me, but when the sales team come to use it the behaviour is different.

The main issue is when a user clicks the email address in profiler to open Engage, a new window opens in the old, dark themed Engage rather than within the iframe as expected.