There were “teething pains” with the Harrier. When Hawker licensed it to McDonnel Douglas (I think), they upgraded it to the Marine AV8B Harrier.
Any cutting edge aircraft, and the Harrier was, Is always going to be more than a little dangerous, especially in the early days when pilots have to learn a whole new way to fly. And of course, so as not to put it all on the pilots shoulders; the designers/engineers had to learn where they screwed up, and fix it.
They call it the bleeding edge for a reason.
A lot of very brave and patriotic men doing that work, especially the test-pilot jobs. Way beyond my pay grade.