I just edited some highly used templates on Commons (among others, PD-old, used
about 30 thousand times, and PD-Art, used about 15 thousand times). When saving,
i got a "sorry we have a problem" error, but checking the template again showed
the edit went though. But looking at Special:Statistics, nothing went into the
job queue. This problem seems to occur consistently with highly used templates.
My guess is that the query used to find pages to update and/or insert them into
the queue takes too long and gets shot down. This problem defeats the purpose of
the job queue, IMHO...
It's critical to a project of mine that this works (see
http://commons.wikimedia.org/wiki/Commons:License_meta-tags is you like). But
also generally, this causes inconsistency in the database. Since we have this
feature, people have started relying on it...