I have struck a few of them over the years, The dreaded spreaded earth contacts of the PDL 60 series.
I still have quite a few of them in my house, must do a loop impedance test on them.
It always seem to be the earths having the problems (longer pin on plug ) or poor beryllium copper which looses it's tensile strength.
Never seen spreaded phase or neutral contacts.
An other fault of these plugs is that they fill up with dust over the years.
