Is AWS documentation feedback broken?

I've tried to send feedback on AWS documents (e.g. https://docs.aws.amazon.com/cloud9/latest/user-guide/setup.html) where the information in the documentation is incorrect, but when submitting feedback and after entering the security catchpa, I end up with a HTTP Status 400 - Bad Request.

The feedback button seems to work ok in an incognito page, but not in my normal browser profile - any pointers as to which cookie is causing things to break?