This error affect Symfony installation with plugin with database tables.
When plugin is installed (tables for plugin created in db) and user run
following error occurs
Duplicate table found: propel
This is caused by duplicated table definition. Once in /config/schema.yml and once in /plugins/PLUGIN_NAME/config/schema.yml.
The solution can be to modify propel-build-schema or propel-build-model task to ignore tables defined in plugins.
Associated forum topic is here: http://www.symfony-project.com/forum/index.php/t/4990/