I had the same problem. Used option 2 in the instructions, and cut off the wiper shaft to use the knurled knobs. Filed flats on the shaft for the setscews. I was very careful not to overtighten the tiny setscrews. The knob would work loose on the shaft, and I would find the setscrews loose. Tightened them a little more, and after 2 or 3 times, the result was as shown in the picture. The knob was stretching in service, causing the screws to come loose. This happened on both sides. I took the knob to work and tested it on the Rockwell C hardness tester - it was so soft it would'nt read on the scale.
I called Saturn - they said they never heard of this before, but to their credit send me a complete new kit. They suggested using JB weld between the shaft and knob. I didn't use JB, but haven't used the wipers since except at inspection time.
Some rainy Saturday, I'll dust off the lathe and make some new wiper shafts since I ruined mine by cutting the ends off. But I haven't fiigured out how to make the tapered knurl at the end. I'd still install the Saturn kit, but avoid installation option 2.