Interesting you should mention this... I have ended up in A&E for this very reason.
Many, many years ago when I had a fleet of Mk1 R5s, I was changing the tailgate on one of them. There are two bolts attaching this mechanism to the tailgate. I removed one and loosened the second. Perhaps I loosened it a little too much as the bolt slipped out allowing the tensioned arm to fly off hitting me in one eyebrow. This lead to me releasing copious amounts of blood from my head although you'll be delighted to hear I lived to tell the tale. And am a bit more careful these days (this was 15 or so years back).