Custom JS gets disabled upon hitting Submit on the form when there are issues with input fields

I have a form in my ZenDesk to which I have applied various custom Javascript/jQuery via the theme's script.js file.  It works fine until I submit the form and there is some problem with it, like mandatory fields not filled out.

The page reloads and the mandatory fields get messages underneath in red like "cannot be blank", however all of the custom JS in script.js also gets disabled.  What is the cause of this, and can it be prevented?  Otherwise it breaks a lot of functionality, if someone submits the form, and then fields are missing, the form refreshes but anything custom in script.js is no longer functional.