Back in my instructor days, there was a 152 which consistently yawed to the right as you entered slow flight, and when you progressed even slower down the power curve, the right wing always dropped in the incipient stage of a spin.
I had other instructors fly this bird to ensure it wasn't my students nervous legs pressing the rudder pedal. Sure enough, they found the same tendecy. Our maintenance looked it over, examined the angle of incidence on each wing, checked the rudder and the trim. All "normal".
We all found this a little odd. This aircraft flew in such state until it reached it's airframe inspection again, when maintenance opened an inspection panel to view the rigging of the aileron. Sure enough there was a wrench wedged in the panel, which caused just enough deflection of the aileron to cause our problems. The controls moved freely, didn't snag during the "free and correct" portion of the checklist, and didn't make a sound when we did spin it. Next time let the maintenace engineers fly your machine immediately after it's out of the shop.....
