Why does my checkbox break after clicking?

I'm creating a simple form with a few checkboxes but now every time I click, the buttons break. It looks like it is include in my script to assign a value of 'no' if a checkbox is not checked but I can't seem to figure out why.

Here is a working demo: http://ift.tt/2dz0Gv7

I have to include this script because i'm importing this form into a separate program and it will not allow me to use this solution:

<input type="hidden" name="checkbox_1" value="no">
<input type="checkbox" name="checkbox_1" value="yes">

What in my script is causing it to break like that?