I had the exact problem that your screenshot shows on some sites that I migrated from an apache server and was able to fix it by turning off Gzip in W3 Total cache.
It happens randomly, right?
Go to https://www.webpagetest.org to test your site, Click the advanced settings, set the number of tests to run to 10 and watch the screenshots that it generates.
W3 total Cache has a total of 4 checkboxes for Gzip, but I believe that the first one unchecks all of them.
If it’s still happening it could be some bad code in your .htaccess file.
Make sure you have “verify rewrite rules” checked under the Miscellaneous settings on the general settings screen (Main Screen).
I would remove all the W3 Total cache code from the .htaccess file and let it reinstall itself.
Good luck!
