Get REST API link display problem from Odoo to UI

Hi guys, I try to GET API from Odoo database with the URL GET API link. The link is working well, but when I add it to the select widget, sometime the data doesnt come out, I have to reload it some times so it can be able to display the data in the UI. 

I bind the link API to a variable and it can display the data well but the UI display. I think it is because of the AngularJS information loading mechanism. Can someone help me with this? Thank you so much.