Ember One to Many relation causing unknown error on console

I'm new to Ember so sorry if it's my wrong doing.

I have an app that was working fine but now I want to connect one of the tables to another in a One to Many relation (one Animal to many ClinicalEpisodes)

Animal model:

App.Animal = DS.Model.extend({
    name: DS.attr('string'),
    clinicalEpisodes: DS.hasMany('App.ClinicalEpisode',{async:true})
});

Clinical Episodes model:

App.ClinicalEpisode = DS.Model.extend({
    animal: DS.belongsTo('App.Animal'),
    clinicalEpisodeType: DS.belongsTo('App.ClinicalEpisode'),
    observations: DS.attr('string'),
});

And when I try to transition to my create template for animals which as always been working I get "unknown problem" in the console and the transition is aborted.

I've tried:

clinicalEpisodes: DS.hasMany('App.ClinicalEpisode',{async:true})

and

clinicalEpisodes: DS.hasMany('clinicalEpisode',{async:true})

Both give the same error.

Any idea why this is happenning? Do I have to change the routes or controllers for this relation to work?