I was replacing the wiper blades on my 2007 SF and found the drivers side wiper arm flapping in the breeze ??? I popped the cap and the 10mm nut was on it's last thread ready to fly off ! I simply tightened it and moved on.......should there be a cotter pin or should I have used some lock tight on it ? I will keep a close eye on it but has this happened to anyone else ?