compressed export file is corrupted (not recognised as gzip)

Hi,

I have created a copy of my WordPress installation on a new server as part of server upgrade.
The content (wp-content and database) is the same on both Site 1 and Site 2 except for the site url.
I used wp-migrate DB on Site 1 to export the database and load into Site 2, no problem there.

When I use wp-migrate DB on Site 2, however the resulted compressed database is corrupted systematically. It’s not recognised by gunzip on Site 1, Site 2 or my Mac.

Setup on both site: Nginx, php-fpm, FastCGI and WordPress 4.3.1, Ubuntu 14.01

The setup difference between Site 1 and Site 2 are:

Site 1:
Server nginx/1.4.6
PHP v5.5.9-1ubuntu4.7
MYSQL v5.5.42

Site 2:
Server nginx/1.8.0
PHP v5.5.9-1ubuntu4.14
MYSQL v5.5.45

(zip, zlib libraries, PHAR versions are the same on both sites)

gzip cli is same version on both servers as well and generate clean gz files.

I feel like it’s more a nginx/config problem rather than this plugin’s, but I’m not sure, and I was wondering if anyone has experienced this before or have any pointers.

(there are no errors in nginx or php-fpm logs)

https://wordpress.org/plugins/wp-migrate-db/