During the annual inspection on our glider, we discovered that the maximum downwards extension of the right aileron (i.e. full left stick) was outside the manufacturer's tolerance. The measured value was 32mm and the manufacturer allows 40mm ± 5mm.
What are the possible causes of a change in the geometry of the system such that the ailerons no longer move in the range they did last year?
For reference, the glider is a 1983 Schleicher ASW19b, with standard l'hotelier control connections and aluminium push rods over bell cranks in the fuselage and wings.