[SOLVED] Maven deploy fails with status 422 unprocessable entity

It has been more than a year since I created this question on GitHub Community; a couple of days after that I found the solution by myself, so I answered my own question, and to this date comments keep being added by people who were helped by my post.  

When I look at it today, I notice that my answer has this particular style, this grumpy indignation which has become so characteristic of me, after a lifetime of battling with lame software, and even worse, with lame error messages. 

I thought I should share this on my blog for posterity.

Here is the link:

The Trouble with XAML Hot Reload in WPF

The XAML Hot Reload feature of WPF is extremely useful because GUI work often involves tweaking visual aspects of an application, so being able to modify XAML, save it, and immediately see the changes on the screen saves a huge amount of time as opposed to having to terminate the application, modify the code, re-compile, re-run, and go clickety-clickety-click to navigate to the same page and finally see your changes.

Unfortunately, as a WPF project grows, the XAML Hot Reload feature inevitably one day stops working: You modify your XAML, you save the XAML file, and yet nothing changes on the screen. The message "No changes were found" appears in the Hot Reload tab of the Visual Studio Output Window, but it is a damned lie, because you just made changes. This can really be a problem.

When you find yourself in this extremely unpleasant situation, here is a list of things to try: