Popup switcharoo

My Resources menu has 4 categories under it. When selecting Resources a tabbed page opens with all 4 categories showing. When selecting an individual category (Recorded demos), a page displays only the Recorded demos.

Here’s the problem: When clicking on a Recorded demo when viewing the Resources page, the demo opens in a popup correctly. However when clicking on one while viewing the Recorded demos page, a popup appears showing another page.

I’ve tried to figure out how to fix this, but am new to WordPress, so don’t know where the offending code is located in my Dashboard (I’ve searched through Appearance > Editor, Pages and Resources, but have not been able to locate it).

Any guidance would be greatly appreciated!