Form validation broken

In customizing our store, I seemed to have somehow broken the form validation. Instead of stopping the form from processing and showing the errors next to the fields, it reloads the page and starts the user over. Obviously this is a major usability flaw. I have tried using a different theme and still get the problem. I tried replacing all the JavaScript files from the original download, still get the problem. Not sure what else to try at this point…

I am using 2.0.12

RESOLVED: I found the problem. I didn’t completely replace all the original JS files as I thought I had. Doing so fixed the issue.