CSS edit rules page does not open I logged in as admin. I opened the css configuration page. I clicked edit rules page. After that, css edit rules page should open but my site is stuck at screen 2(home page). After I click edit rules many times, sometimes, I get the edit rules page. I feel that this is a site wide issue not css injector issue. 

Example: If I click Save on views page, it does save but my page gets stuck at the home page. I have to hit the back button to come back to view and I see that views is already saved. 

If I click clear cache in performance page, I have similar issue. It does clear the cache but the site is stuck at home page. I hit back button to come back to performance page again. 

I simply do not know where to start troubleshooting. I am not getting any error messages. If you could point me to right direction to solve this issue, it would be very helpful.

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Screen2:
Turned off overlay module. Problem has fixed.