Ajax even of jquery not working for 1 single dropdown


Please go here:

First select any size
The select Product Paper …

You will see that if you select any of the 1st two options in Product Paper then the loading gif circle stays and does not goes away. Where as if you select 3rd option i.e: “Silk Coated” then it goes away. This is only happening with this dropdown and rest all are working fine.

What is the issue ?