When i used Gii to create the model class, i forgot to change the pre-filled namespace in the Gii Generator field for the Category model from ‘app\models’ to ‘backend\models’.
Since ‘app\models’ is automatically filled even if you’re using the advanced template, this is maybe something for the developers to take a look at?
I was having the same problem with the advanced template in 2.0.2. The name space defaults to app\models and changing it to frontend\models worked fine.