My dd also taught English overseas - in SE Asia and Australia. She had done a very rigorous full time TEFL course first, and was appalled to find that some of her fellow teachers - Brit or Aussie- were making basic mistakes.
She once had students from someone else's class worriedly asking her about something basic (e.g. there/their) that was confusing them, since their teacher had got it wrong on the whiteboard.
When she pointed it out to their teacher, he just scoffed and said nobody cared about such things any more, it didn't matter.
But it did - the poor students were paying good money for their lessons, and were going to take important exams, where such mistakes would mean losing marks.
She found such occurrences acutely embarrassing. It was usually the case that such teachers had done a cheap online course, where unless you really made a complete hash of it, you would get some sort of 'qualification' at the end.