H Peacock
I can imagine a number of possibilities:
Publicising the issue does not mean that everybody has read the published document. Those who signed that they had read it might NOT have read it, or they signed but did mot understand or think about the significance, or forgot about it after a month or so.
A very junior engineer might have been told to insert the pin, and got it wrong.
A non-787 engineer, helping out his mates who had a high workload, might have got it wrong.
The tug driver, or another non-engineer ramp worker might have inserted the pin and put it in the wrong hole.
An engineer, asked to check all the pins were in before the test might have seen the pin flag and thought the pin was in - they might not have gone right up to it to check the pin was actually in the correct hole.
Sadly, I don't think that in these days of reduced training and costs that we can assume that everyone - even pilots and engineers - necessarily understand simple physics, nor that everyone can see and understand by looking, how a series of undercarriage struts and levers work.
As a pilot, I was never shown where to fit the locking pins on any of the 7 commercial passenger aircraft types I have flown. Yes, it might be written in the FCOM, but you can't beat actually being shown stuff on the actual aircraft. Have all engineers and tow crews been actually shown exactly where to fit the pins?
It should not be physically possible to insert a ground-lock pin in the wrong hole. If it is, that is very poor design, because with the best will in the World, if something mechanical can be done wrong, it eventually will be.
Engineers only have mandatory duplicate inspections on certain items, such as engine oil caps.