When there are ambiguous relations clicking to select one or the other does nothing. This bug affected only our production server, devel and debug worked well. This is weird, and I think we are encountering the strange behavior described in http://yuilibrary.com/projects/yui3/ticket/2532993 or similar: in some situation (e.g. our production server, where js files are minified/compressed) using the "on" method on NodeList does not work. I am confused about the real reason for this bug. However, the documentation says that we should avoid using NodeList.on, in favor of using event delegation, that is exactly what I did in this branch. Tests are not included: we have a specific card for adding tests for the relation module.