When a package is checked out by a user, other users are able to undo checkout or perform check in of the same package. It is reporting an error when clicking the undo check-out:
"Error while attempting to undo checkout file filename from project projectname : svn: package script is not locked in this working copy."
WORKAROUND
none
STATUS
Issue fixed in version 12.1. The latest version of Toad for Oracle can be downloaded here