Contracts in China are not worth the paper printed on: On hundreds of occasions the principal/owner has stood in front of the teacher spewing "interpretations" in terminology to alter what was printed. Again: Chinese persons do not make contracts with other Chinese persons because they do not honor the contracts. Most of these persons who make these contracts do so only because in western countries it's customary to "contract" a person for positions that are long term. Not always, but customary. The people you libel as: substance abusers, under qualified, psychiatric issues, and other vague observations are Phds of Education, Law, Business and Finance, and other fields. Our investigations have revealed Universities behaving in the most unprofessional manner so as to push out the most qualified of teachers. You also infer there's no "bait and switch". If you've been in China for 10 yrs you've no doubt had contact with qualified teachers who were brought in to teach a particular subject and were then told it wasn't available but can they teach: physics, math, and other subjects. One particular teacher we interviewed now works for the U.S. Embassy in Beijing who was not paid for months and when they complained were accused of "being a bad teacher who causes many problems". After the teacher left the school the person was blacklisted. If a teacher files a complaint with the PSB in that district the school pays the back salary and provides the documents they are required by China law. Your statement regarding contracts is ludicrous on it's face and ridiculous in it's scope. The contracts are usually written by western persons and altered by the school. In 80% of contracts signed by teachers there's no counter-signature on the document so as to not make it legally binding. Students are respectful: maybe a small percentage but most are rude, sleeping, playing with their mobiles and on more that one occasion violent. Not very often violent but teachers have been attacked and killed. The most glaring example of this was Hilary St. John Bower who was murdered and dismembered by his mainland China fiancee after closing a land deal for her in Hong Kong. Students have attacked other qualified teachers for things such as not speaking in Mandarin. The Chinese populace see nothing wrong with attacking foreigners and have been quoted as such. Members of our group have had friends who were Phds and attacked with knives or beaten and left unconscious on sidewalks. Your comments smack as a Chinese national defending the so-called "purge". We doubt the intention and message in your writing. China can be a good experience if you're lucky and not exposed to shady practitioners or dangerous situations. But since these people don't have a sign on their foreheads as a warning we better suggest teaching in other countries where the money is better and the position is safer.

It is difficult to dispute "9 facts" organized as "A, B, C, D".
Contracts are a legal construct of individual nations. As a foreign employee in any country, you would be mistaken to interpret your host nation's contract as being equivalent to your native country's. It is not.
I worked for a decade at six employers in four cities in four provinces in China. Five universities, three public/ two private, and one privately owned language center. I was never paid late. Not once. Additional classes were only added upon my approval and I never was assigned to work at a 'satellite' location. It is important to note that I never located or accepted a job with an agency or recruiter. I would suggest that your litany of complaints are substantially a result of agency/recruiter practices.
China has far fewer foreign teachers than it had when I first arrived. I would not call this an "exodus"; I consider it a purge. Most of my foreign teacher colleagues were incompetent. Almost all were uncredentialled. A significant portion were suffering from psychiatric difficulties and substance abuse. It is fortunate that they are no longer given classroom time with students.
I believe that the responsibility for the poor quality of foreign teachers in China falls directly on the employers, the immigration laws, and police enforcement. China has been attempting to clean up its language education industry with variable results. Foreign teachers with genuine teaching credentials that contract directly with universities in China are likely to have a positive, if challenging, opportunity to interact with students who are more respectful and more grateful than they are likely to find in Western countries. Foreign teachers should not mistake teaching in China as a career; it is not. But it can be an amazing and valuable life experience.
It was for me.