Test question feedback problem in Firefox

I am revising our end-of-course tests to show immediate custom feedback via the "Display feedback with popup window" option rather than using the end-of-test feedback that Lectora generates. The pop-up window feedback works fine in all browsers but Firefox. Here's the problem: In all other browsers, the course advances to the next test question when the pop-up window is closed (as it does with the "Display Message" feature). The course doesn't auto-advance to the next question in Firefox though, requiring a separate action to advance to the next screen. Anyone have thoughts on why this is happening along with suggestions? Again, this is only happening in Firefox.

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