We're running multiple WP installations on a VPS running Centos 7. A week ago all image uploads on all installations stopped, all we got was the HTTP Error during upload. I googled my way through a dozen instructions to fix it and none worked - then I tried restarting httpd on the server and it started working.
We had not touched the server since then, but yesterday it happened again - and httpd restart helped again. We have NewRelic running on the box and the server load & cpu usage are low and there's lots of disk space & memory available even during the error. Neither the access log or error log give any hints.
Does the httpd restart fix point to any direction?