When I was a senior full time instructor I was the guy who got the "problem" students from junior instructors, almost always the issue was "they can't land". The first thing I did was go to the practice area and then starting at a nose up attitude slowly pitched down and asked the student to tell me when the aircraft was in the level flight attitude. I then covered the airspeed indicator and asked them to show me the climb attitude they would set after takeoff and then the the 65 kt landing configuration final approach attitude. A discouragingly large percentage of the "problem" students failed at all three tasks. The problem was not that they couldn't land it was that they could not fly period.
Sadly these students instructors utterly failed them at teaching the most important part of the PPL syllabus; teaching the foundation skills ( attitudes and movements, straight and level, turns, and climbs and descents).
On a separate note I told all my students that flying instruction had to work for both of us. If my personality was getting in the way of the training I made it clear we needed to talk and I was totally OK with them requesting another instructor. Similarly I passed on a few students to another instructor who I felt was a better match. I also refused to continue teaching a few students who were not interested in putting in the effort to learn.