LMS not registering SCORM2004 score/SL3

Hi all. I've got an LMS/SCORM issue I'd like your thoughts on please. 

Here's how our LMS works:

To open an e-learning in our corporate LMS, the user must navigate to the course page, then click on a link which will open the SCORM object in a separate window. Once the course is complete, the user closes the SCORM window and the final scores etc. are delivered to the LMS window, which refreshes in a few seconds to show said score. Pretty standard I'd guess. 

 

Here's my problem:

Randomly, users are reporting that the LMS doesn't refresh and display the score. It just 'freezes' on the screen saying "Collecting data". When they resume the course they often discover that only half of the course is registered as complete despite them having already finished it. 

 My theory:

I'm wondering if local network settings, or perhaps PC settings are cutting off the internet connection half-way through the e-learning, thinking that there is no activity? Or simply a super slow internet connection (it must be random, because network speed tests are good) Or, perhaps our LMS is going to sleep? 

 

If anyone has any ideas on how I could collect information that might help me get to the bottom of this, I'd appreciate it hugely. Thanks in advance.