This ticket had assigned some Differential requests:
D228

OK, I've been doing some digging here and I think the bug is in the updates sync code.

When we sync an update, the sync(updateinfo, milestone) method is called on the update object. I don't recall why we're specifying the update's milestone but I do know that we're not setting that correctly:

lang=python, name=update_sync.py, lines=14, counterexample
for update in updates:
self.log.debug('running sync for update %s' % update['title'])
existing_update = Update.query.filter_by(
title=update['title']).first()
if existing_update:
self.log.debug(
'syncing existing update %s' % existing_update.title)
existing_update.sync(update, bug.milestone)
else:
self.log.debug('creating new update %s' % update['title'])
existing_update = Update.from_data(update, release,
bug.milestone)
self.db.session.add(existing_update)
self.db.session.commit()

the bug referenced in bug.milestone is not coming from any bug that's related to the sync process and thus, is not set properly. in my dev instance, that ends up being 'f21-final' but I'm not quite sure what that's being set to in production.

Still working on a fix proposal but wanted to update with what I've found thus far.

Closed by commit rBLKRf1085b035763.