@Sytek Edit - The Duet freezes without the thermal warnings and the stack underflow command. The commands I'm sending to the Duet from the PanelDue are just Move and M408: Report JSON. The config file was made quite along time ago and the firmware was recently updated.
Really happy that you were able to do that as a web developer beginner! Thanks for the url, it really details the body as I wanted. The issue with using the network monitor to view the request/responses is that you only observe some options and not all of them. Sure it's a way to get some information but you can actually be missing a lot of it.
Are you interested in working on something together? I'm beginning a living on software engineer but would love to create something with others and share it. If you want to join me, let me know.
That would be great as long as you can tolerate a beginner! Not sure how much use I would be. I am on github, same username.