The is obviously an issue in your controller. When the data is being passed to it, something is amiss with what's you are trying to do.

When you go to response in dev tools, what error are you getting?

I'm getting an internal server error. Error 500.

Yeah, but what is the error? 500 is a server error, so it can't process. Laravel gives you useful helpers to point out what the actual error is. Make sure debugging is on in app/local/app.php (if your environment is set up, if not just app/app.php)

Check your log in app/storage/Laravel.log

Or you should see the error in JSON format when you view the response tab of chrome dev tools.

These last two point should reveal what is causing the 500 error.

What browser are you using for this test?

Another way to test this, and is kinda a good approach, is to test the form submits without any ajax calls, then add it in after you have it working. Although this isn't always possible when doing drag and drop stuff.

Hope that helps.

It's probably a CRSF token error