We recently updated to 4.7.4 in an attempt to resolve some issues we were facing, in the end we found another fix for that problem.
But since the update we have been experiencing 502 Bad Gateway ("The server returned an invalid or incomplete response.") errors, they seem to randomly occur on any pages that use Civi but not on any of the normal Wordpress pages in the site.
Our Civi install sits behind a haproxy load balancer so its possible this is concealing the true cause of the issues and error messages.
Has anybody else experienced any issues like this on 4.7.4. or any of the other recent versions? As I said the 502 could be a misdirect from our load balancer so other suggestions as to causes would be equally appreciated.
Any suggestions as to causes would be appreciated as I'm drawing a blank myself!