WordPress / EasyEngine failed to start after server reboot
Does your WordPress sites just went offline after a VPS reboot or server status change?
When to use custom post types in WordPress
It's not your fault to think that custom post types are confusing; it's WordPress's.
How to fix “The uploaded file could not be moved to wp-content/uploads/” in WordPress
Most likely, it's due to the web server's worker processes belonging to a different user that has no file ownership.