RailsAdmin & Rake are not good friends
RailsAdmin skips its initialization when your Rails environment is started from a Rake task. This seems like it might be good in theory, unless of course your production app is started through a Rake task.
This does not stop RailsAdmin from working, it just doesn't do all the initialization, including any custom Authorization logic you may have defined. It seems like this has the potential for being very bad.