Not the greatest photo, but it may show that the pin is basically parallel all the way from the retaining pin hole to the far end, which has a taper at the last few millimetres.
Mine have all worn as you describe, the pad wears away at the pin, creating a notch in it. The pad then catches in that notch. Replace the pin every time you put new pads in; or, rotate it 180 degrees and replace every second set
Mine have all worn as you describe, the pad wears away at the pin, creating a notch in it. The pad then catches in that notch. Replace the pin every time you put new pads in; or, rotate it 180 degrees and replace every second set