I've been working on something on/off for a while & have used a number of "Dupont" jumpers (against my common sense to just solder wires!!). Noticed was recently getting some extremely strange results, that hadn't noticed before (or was I overlooking it?)...After much fussing & diagnostics, found that several of the jumpers were extremely loose. They'd fall off the pins if you waved a sheet of paper at them...this is NOT how they went on originally (nice & tight)...wear & tear from installing & disconnecting & occasional tug (oops) on the wire did them in.
So why'd they loosen up SO badly? Well, according to my magnet, theses are made of steel, rather than springy metal such as beryllium copper. I have piles of various flavor of these (male, female, long short, etc). Probably 1/2 to 3/4 would hang themselves by the magnet. The others did not. I think all these junkers are gonna hit the trash can, don't have time to waste on such madness...why would they use steel terminals like these? Is this common with connectors now? Big trouble brewing in connector land!!!