On a WP 4.5.3 multisite network of 60 sites, we recently began experiencing a LOT of 500 Internal Server Errors, especially when editing posts and pages.
The errors can be seen in the Browser console and they all reference:
POST http://soobahkdo.biz/wp-admin/admin-ajax.php 500 (Internal Server Error)
Each 500 error may have additional references listed for different plugins, wordpress functions, etc., etc.
Near the same time we also began experiencing quite a few of these errors:
POST http://soobahkdo.biz/wp-admin/admin-ajax.php net::ERR_CONTENT_DECODING_FAILED
I am not sure how to interpret what the console errors are telling me.
In the admin area the browser console errors are very evident when pages are loading or features are used.
I have tried most of the traditional troubleshooting techniques like eliminating plugins, etc without success.
Editing posts and pages and other things work ok part of the time and hang up at other times. Selecting media for insertion may fail and inserting images in the post editor window may fail intermittently and setting the featured image may fail intermittently. When those failures occur there are multiple 500 Server Errors in the console and/or Content Decoding Failed Errors. Sometime refreshing the page will resolve the issue for a while.
Please DO NOT suggest upgrading to 4.6 right now. We probably will within a month, but we need to allow time for all the plugin and theme crews to catch up before we make that change.
Any assistance will be appreciated.