How to debug a bootstrap/jquery problem

So I've got a site that runs a bunch of subdomains. Here's an example



When a user goes to login they click on the login button and get a drop down



Now that's all worked just fine for a few years but I've needed to run some Auth backend changes and had to change the post settings on the form etc but not much has changed.

All of a sudden any click on the dropdown causes it to close instantly which means users can't login. Nothing shows in the Console, bootstrap has a bunch of listeners but nothing new AFAIK.

How do I debug this to find out what is causing the close?

 

Thanks for that, I ended up using an extension called jQuery Audit which adds extra info in but I hadn't considered getting an extension to the developer tools.