Interesting.My Dad bought a 2-ton motomaster jack 20 years ago when I was just a kid and it's still going strong. I routinely borrow his jack (and the stands) when I need to work on my truck's suspension (stupid IFS!) Easily one of the more reliable pieces of kit in the garage!
Usually the pin that holds the two pieces of the handle together. I've had 4 of them. Every single one has broken. Currently I just found a bolt lieing around to ifx the 2 that I have as I got fed up returning them. The other one just has no pin so the handle falls apart if you pull on it.