While trying to troubleshoot a client’s website I kept seeing this message when trying to access the Page Menu / Edit a page.
This page isn't working ____ didn't send any data. ERR_EMPTY_RESPONSE
Turns out the issue was triggered by the Visual Composer plugin.
In apache/.htaccess I increased the SubstituteMaxLineLength level to 10M, the default setting is 1M.
<IfModule mod_substitute.c> SubstituteMaxLineLength 10M </IfModule>
The website was hosted on GoDaddy.