Changing domain name failed, on just one site

Hello,

I have been using this plugin very successfully to migrate several new sites’ dev databases to their productions sites, when they are ready to launch.

I copy all the files to the new server root, mysqldump the dev database, import that dump file into an empty fresh production database, and then put a temporary override on the sitename and home url in the wp-config.php file in the production directory. (http://codex.wordpress.org/Changing_The_Site_URL).

Then, I also go to Tools->Migration Assistant (the plugin is already activated before the transfer), and just run the Change Domain Name function, change dev.example.com to http://www.example.com (for instance).

This has worked for dozens of sites, but now a new site that needs to launch later this week, when I try to test this, I get this error message:

Failure!
An error occured while changing instances of your domain name. Rolling back to the previous state also failed. Please try importing the database backup stored under the backup folder manually.

The only two things I can think are different are these:

1. the server both of these are hosting on is an Ubuntu VM running in Microsoft’s Azure cloud, instead of our normal Ubuntu VM’s, which are usually in some sort of “linux all the way down” system.
2. The development server’s URL starts with “staging” as the subdomain, instead of “dev” for reasons specific to this customer, so I am trying to change from a name of a different length (“staging…” to “www…”)

I have WordPress debug.log turned on but there’s nothing in it about this, and no other PHP error_log files are being generated.

https://wordpress.org/plugins/wordpress-move/