Thanks for the info Rolsmith, sorry to hear that your confidence has been dented.
It is easy to say that torquing the nut up wrongly is the cause, but a well fitted spline should not rely on the securing nut to do any more than prevent longitudinal movement. For example the splines in a gearbox allow the selector dogs to move freely on the splined shafts and they survive well enough.
More thought required here methinks.
Phil
