"To me, this sort of teaching is representative of someone who didn't learn the basics properly and has got through the rest of the training without revising his/her incorrect base facts"
So that means that this individual may have got it wrong at PPL training and then received the wrong info during CPL training and during instructor training and at no stage has this ever been picked up.
This individual must have done the stalling exercise on at least 1 instructor renewal test so the FIE must have missed it.
However, leaving the individual case behind, what system is in place for instructor quality control. i.e. do the CAA actively seek reports of the above or do they rely on the instructor/examminer/FIC/CFI to effectively quality control themselves?
Regards,
DFC