drush up updates module then restores from backup

Running against Drupal 7.22, on OSX 10.7.5, updating a contrib module works until the end of the process when the original is restored from backup with no indication as to why. (I'm using git locally for version control).

16:12:45 myusername:~/Sites/drupal-7.22/sites/mysite.local $ drush up -v --yes fontyourface
Initialized Drupal 7.22 root directory at /Users/myusername/Sites/drupal-7.22 [notice]
Initialized Drupal site mysite.local at sites/mysite.local [notice]
Loading release_info engine. [notice]
Loading version_control engine. [notice]
Loading package_handler engine. [notice]
Executing: wget --version
/usr/bin/php /Users/myusername/drush-8.x/drush.php --php=/usr/bin/php --backend=2 --verbose --yes --root=/Users/myusername/Sites/drupal-7.22 [notice]
--uri=http://mysite.local pm-updatestatus fontyourface 2>&1
Initialized Drupal 7.22 root directory at /Users/myusername/Sites/drupal-7.22 [notice]
Initialized Drupal site mysite.local at sites/mysite.local [notice]
Loading outputformat engine. [notice]
/usr/bin/php /Users/myusername/drush-8.x/drush.php --php=/usr/bin/php --backend=2 --verbose --yes --root=/Users/myusername/Sites/drupal-7.22 [notice]
--uri=http://mysite.local batch-process 89 89 2>&1
Initialized Drupal 7.22 root directory at /Users/myusername/Sites/drupal-7.22 [notice]
Initialized Drupal site mysite.local at sites/mysite.local [notice]
Checking available update data ... [ok]
Command dispatch complete [notice]
Name Installed Version Proposed version Message
@font-your-face (fontyourface) 7.x-2.7 7.x-2.8 Update available

Command dispatch complete [notice]
Update information last refreshed: Wed, 05/01/2013 - 16:12

Update status information on all installed and enabled Drupal projects:
Code updates will be made to the following projects: @font-your-face [fontyourface-7.x-2.8]

Note: A backup of your project will be stored to backups directory if it is not managed by a supported version control system.
Note: If you have made any modifications to any file that belongs to one of these projects, you will have to migrate those modifications after updating.
Do you really want to continue with the update process? (y/n): y
Starting to update @font-your-face code at sites/mysite.local/modules/fontyourface... [notice]
Executing: svn info /Users/myusername/Sites/drupal-7.22/sites/mysite.local/modules/fontyourface
Executing: bzr root /Users/myusername/Sites/drupal-7.22/sites/mysite.local/modules/fontyourface
Executing: wget --version
Executing: wget -q --timeout=30 -O /private/tmp/download_file5TlUZc http://ftp.drupal.org/files/projects/fontyourface-7.x-2.8.tar.gz
Downloading fontyourface-7.x-2.8.tar.gz was successful. [notice]
Md5 checksum of fontyourface-7.x-2.8.tar.gz verified. [notice]
Mime type for /Users/myusername/Sites/drupal-7.22/sites/mysite.local/modules/fontyourface-7.x-2.8.tar.gz is application/x-gzip [notice]
Executing: tar -C /Users/myusername/Sites/drupal-7.22/sites/mysite.local/modules -xzf fontyourface-7.x-2.8.tar.gz
Executing: tar -tzf fontyourface-7.x-2.8.tar.gz
Project fontyourface was updated successfully. Installed version is now 7.x-2.8.
Backups were saved into the directory /Users/myusername/drush-backups/mysite2/20130501041256/modules/fontyourface. [ok]
Rolling back update of @font-your-face code ... [notice]
Executing: svn info sites/mysite.local/modules/fontyourface
Executing: bzr root sites/mysite.local/modules/fontyourface
Backups were restored successfully. [ok]
Command dispatch complete [notice]
Command dispatch complete [notice]
16:13:05 myusername:~/Sites/drupal-7.22/sites/mysite.local $ drush pml | grep 'font'
@font-your-face @font-your-face (fontyourface) Module Enabled 7.x-2.7