Dashboard Authentication - Basic Auth Prompt keeps popping up

We have implemented hangfire in an internal (OWIN) application.
I have read the docs about using Authorization Filters to enable dashboard access from non local machines.

I have created a custom Authorization Filter which inherits from IAuthorizationFilter and implements the Authorize method. The method validates the OAuth authentication implementation we are using with our application. It successfully returns true for valid users and I can hit the dashboard from non local machines.

However - the “Authentication Required” box pops up a couple times when hitting the dashboard and on any subsequent clicks within the dashboard. The dashboard has full functionality (after clicking “cancel” to view it properly). It seems the Authorization Filter is working correctly and the “Authentication Required” box does not have relevance in terms of viewing/using the dashboard.

But it is REALLY annoying.

Can someone please assist me in getting around this?

Thanks so much in advance.

UPDATE: I moved the application to a new server and I am not having this issue.
I would still like to know the cause (guessing something with IIS?) So I can document it for my team for future issues.