CMS Pages/Blocks not loading in backend

[mo0klin]

Just installed 2.0.2 through the guide at http://devdocs.magento.com/guides/v2.0/release-notes/tech_bull_201-upgrade.html

Whenever I go to CMS - Pages or CMS - Blocks it's not loading the current pages/blocks. The spinner just keeps loading. I can add a new page/block with the button, but whenever I try to save it, it also keeps spinning and saying Please wait...

[mo0klin]

Seems all options in the backend where not saving and stuck in the Please wait... loop

Did a full system/server restart, and looks like everything is working again.

[Metalmania]

Looks like I am getting the same problem too, however I'm on a shared hosting server, so I haven't got the option of a server restart!

It seems I can Add a Category but I can't Save any changes to the Store -> Configuration settings, the Save Config button just doesn't do anything.

[greg3000]

I also have this problem after upgrading to 2.1.2, and rebooting the server doesn't fix it.  

[TOM_M_]

I also have the same problem any clues on how to fix it?
It just happened outta nowhere I have not changed anything and all other backend pages work fine.

[guilherme_correia]

Same issue here. No apparent reason to trigger it. 
Has anyone found a fix for it yet?

[guilherme_correia]

I started looking into server problems regarding this issue and found out that PageSpeed for Nginx was causing this issue ( All minify, etc., options on magento2 are disabled ).

Disabling it solved my issue.

I wonder if I can replicate this issue with my exact server configuration on the cleanest magento 2.2.2 installation and PageSpeed for Nginx on, since I also have Magento 1.9 running on the server with no issues whatsoever regarding this particular module

[fellipe_vicente dos santos]

Hi guilherme, how did you disabled Nginx pagespeed?

Can you lend us a hand on that?