[Observium] discovery.php repeatedly trying to upgrade database

I did an svn up recently, and am now at r2879. I ran discovery.php to update the database afterwards, and it went fine; however, now my discovery.php processes hang trying to install old database updates:

$ ./discovery.php -h new Observium v0.12.2.2879 Discovery

-- Updating database schema 000 -> 001 ... done (0 errors). 001 -> 002 ...

The result is the discovery.php processes stack up and eventually exceed the database connection limit. Any ideas on why it persists on trying to update my already up-to-date database?