Course Published with Articulate Storyline 2, Freezes When Next Button is Clicked

A course that my team deployed over six months ago is freezing for a small group of individuals that are located in the same office. There was one other office in another location that experienced the same thing, but it has been a long time ago, and we were able to come up with a work-around at the time. Other than the two offices no one has had trouble with the course. There have been 273 start the course, 215 complete it, and 75 are still in progress. Students are located all over the United States. My team is unable to replicate the screen freeze, but we were able to do a screen share with them and launch the course in debug mode. 

I've attached two documents. One is the debug log from the screen share. The other is a debug log I captured, following the same path, on my computer. The freeze occurs in IE 11 and Chrome. They did not have FireFox, so we were unable to launch it in FireFox, on their computer.

Just a couple of things to note about the attached documents. The "LearnersProblematicIsolatedDebugLogNextClickOnly.doc" is the log from their computer, and reflects what's occurring under the hood, when their browser freezes. I went through both documents and Bolded and Highlighted in RED, the lines that were very different than anything in the normal and healthy debug log. 

Here's the user path that results in a freeze.

1. The student launches the course.
2. The student then clicks a custom button to go to the next page.
3. The student is successfully taken to the next page, (page 2 in the course).
4. The student clicks Next.
5. The course freezes.
6. The student waits, sometimes for over 2 minutes, thinking it may eventually unfreeze, but alas, it doesn't.

It appears to me, according to the debug log, that when they click Next, the course starts trying to exit. The student never clicks the close or exit button, but it's as if the course starts to receive variable values that would seem to indicate the user clicked exit, though they didn't. But the course does not have all the necessary variables set to successfully exit, and so waits for the variables. The variables the course is waiting for, never come, so the course freezes.

Has anyone experienced anything similar? Or does anyone know what might be the cause? 

I read something in a blog post about Norton antivirus software causing things like this. Also, I know that sometimes Flash Player's security settings require the user to give specific permission to a domain attempting to play an older swf or flv file, since the older Flash files did not provide as much security as swf and video files published or encoded in newer versions of Flash. This should not be the case with this course, as it was published with Storyline 2. 

Any thoughts? Anyone know what's happening in this instance?

Thank you so much!