Ember model attribute is disappear

I am using ancient version of ember: "ember-cli": "^0.2.1"

When I load page first time, everything is good. But when I hit back on browser and go back and again click to same link and reopen page, my model attribute is empty Here is my property looks

duration: Ember.computed.alias('model.duration'),

duration is coming 0 when I open it second time. However, I can see it on rest API reply, and when I console.log I can access it like:

this.get('model')._data.duration;

Please help, this issue braking entire application