I did a fresh Drupal(v7.39) installation on Nginx server. Everything seem fine until the WordPress Migration process with "Migrate", "WordPress Migrate", and "Migrate Extras" modules. The error message I got is
An AJAX HTTP error occurred. HTTP Result Code: 502 Debugging information follows. Path: /batch?id=83&op=do StatusText: Bad Gateway ResponseText: 502 Bad Gateway 502 Bad Gateway nginx.
Even I got an error, all the content did migrate correctly except the url alias. The URL was set for "Set path aliases to their original WordPress values" during the process, but they came out like node/101, node/103....
What may causing the error and how can I fix this?