Feed Tamper (apparently) not running with drupal-queue and cron invocations?

I am running the latest versions of Feeds, Feeds Tamper, Drush (4.x branch) and Drupal (as well as PHP 5.3, though I don't believe that's important).

Anyway, Feeds Tamper works beautifully for me when I import a feed through the Feeds administration interface, and when updates were just being triggered via Poormanscron.

Recently, some of my feeds became too large to manage through Poormanscron, and I switched to using my crontab to call the drush commands for queueing feeds using drupal queue and for running cron (a copy of my crontab is below).

0,15,30,45 * * * * /usr/local/lib/drush/drush -r /var/www/MYSITE.com queue-cron
7,22,37,52 * * * * /usr/local/lib/drush/drush -r /var/www/MYSITE.com cron

The cron commands are running, and my feeds are being updated, but it seems like my Feeds Tamper edits are no longer taking place - nodes are showing up un-edited.

Any thoughts as to what could be going on?