Edge loads in Internet Explorer Mode -- sometimes?

We're working on a webapp. We've noticed this set of oddly contradictory behaviors in test:

• When going to the website through Novell Access Manager(NAM) using Edge, the page loads in Internet Explorer Mode and does not render properly.
• When going to the website outside NAM using Edge, the page works fine (does not use IE Mode).
• When going to the website through NAM using Chrome, the page works fine.
• Only about half of the co-workers I polled to try this experienced the problem. Meaning half worked even through NAM and Edge. This is a network setup of edge and our versions and property settings are identical as far as I can tell.

Yes, we cleared cache, restarted edge, and reloaded the page. Most of the online help I find about IE Mode is how to turn it on or off from the browser, but our user base isn't going to control their installations (nor do we). Why is my website triggering this...sometimes? Only through NAM, only with Edge, and even then, not everyone? Note - those with the issue CONSISTENTLY get the issue.

I'm struggling to even diagnose what's going on because I can't get into devtools on the affected browsers since IE Mode shuts off devtools, and I don't seem to have this "IEChooser" app the message tells me about. So I'm struggling with even where to look. Any ideas what to even check?

We eventually determined that there was a networking policy applied to our systems that specified the domain as being one that should use ie11. That's why it wasn't seen in our browser settings, and why it behaved differently between people. We don't know WHY the policy was applied, probably some test someone was doing. We also don't know why some people and not others or why it was left in place. But once it was lifted, Edge worked as expected.