sometimes the wiper comes loose but the owner didnt stop the wiper drive quick enough so the aluminum wiper arm splines get munched by the steel spindle splines.

a wavy washer fits under the AL nut. the OD of the wave washer is small enough to fit in the recess of the wiper arm.

dont forget to clean the shaved AL from teh steel spindle splines

This is an easy fix. Get a very small triangular-shaped metal file and deepen all the splines on the wipeR arm. it is soFt aluminum and this works pretty well to get the wiper back on the wiper-pivot. use the original nut and washer.

i can not agree with removing additional material

I had that happen on a Ghia. Wrapped a strip of aluminum foil around the shaft then pulled the arm down on the shaft with the nut. IIRC, I had to do it twice to "build it up". Held till I sold it 13 yr's later.