When i duplicate a snippet, give it a new name and save it. The snippet does not show up in the doctree.
But when i try to do this again. the manager says there already is a snippet with that name.
Turn the cache_db setting off (or manually choose Clear Cache after saving any changes in the manager) and the problem should go away. There are some significant issues with the database result set caching in the 2.1.x releases that have been addressed for the upcoming 2.2.0-rc1 release (see the nightlies if you want to test it out).