As for a foreigner NOT in serious trouble respecting the cultural pattern by overlooking major incompetence,he(or she) might well not have sufficient patience to do so.
And after that foreigner has made an incompetent school waiban,for example,lose face,it'll only be a matter of time before the latter will try to get revenge by fault-finding,even though those identified shortcomings are not serious in nature.
When things have got as bad as that,that foreigner won't be able to get his(or her)teaching contract renewed.Instead he(or she) can secure another teaching post with the help of a USABLE testimonial issued by his(or her) current employer even though the foreign teacher may only be one of average or slightly below average ability.Even incompetent foreign teachers who complain regularly about minor things have also been given such testimonials.By and large it is the case that the current employer doesn't care what catastrophes in terms of Chinese teachers losing face or bad teaching might occur at a foreign teacher's next workplace.Even worse,a foreign teacher who has been teaching in China for just a year or two can find a new post without any testimonials at all provided he(or she)is not coloured or Filipino.
And so the losing of face by Chinese teachers and bad teaching by foreigners can go on and on.