Ajax calls in IE 11 issue

Hello everyone.

I've encountered an issue with the ajax calls on IE 11 (other browsers are ok and on other versions of IE I'm testing through a virtual machine and I can't reproduce it in those conditions). I have an application with a lot of ajax usage and I've noticed that when I work on IE 11 something strange happens.

The test scenario for me is this: I use my application on IE 11, then open another windows application (basically I need to lose focus of the IE page) and after a few minutes I return to the IE window. The first usage of ajax will take a really long time (20 seconds or even more). After that everything is ok, as long as I stay on the IE window.

I found a rather dumb fix for this. I created a script on my application that calls a dummy page every minute through ajax. It works for the time being, but I'm not satisfied with this solution. Has anyone encountered this or has some idea what could cause this?

Thank you

Ajax calls in IE 11 issue