Just a quick solution for those that having problem on DNN modules without knowing why. Just turn off of the DNN Gzip compression and I would recommend you to use Page Blaster from Snapsis.
This compression issue has been first known in DNN 5.6 and still occurring in DNN 6.0.1. However, it cannot be reproduced thus cannot be fixed as explained by DNN Core team.
So here some of the known issue once you turn on DNN Gzip compression:
1. FAQ module – It AJAX content load and expand will stop working after certain time.
2. File Manager – It’s Ajax folder expand will stop working.
3. DNN site cannot be loaded and showing this error message in your browser: Content Encoding Error – the page you are trying to view cannot be show because it uses an invalid or unsupported form of compression
4. DNN Map Module – If Gzip is turned on, you will see the module is keep fetching data without any success.
There are some other issues in other modules as discussed in the DNN forum…so whenever your DNN start acting weird, just turn off the DNN Gzip compression and see if it fixes the problem.