Interesting...
To clarify for the benefit of Sirpeterhardingslovechild in post #177, if the handle is displaced from its housing with the seat pan pin out, the pin will not go back in the correct hole. End of.
Which 'correct hole'? The correct hole in the handle, or the correct hole in the collar around the handle?
I hope this clarifies for those who have a little bit of (dangerous) knowledge. I find the level of amateur speculation here appalling.
I think all you did was muddy the water there with a bit of speculation. Sean's pin was in the correct hole on the handle, not in a gap between handle and seat. However because the handle had been pulled upwards the hole in the handle was above the level of the collar so there was nothing preventing the final pull.