Those are not Molex brand connectors.
I agree.
The metal alloy used appears to have work hardened and become brittle. I don't see any evidence of melting. Repeated cycles of mating has done the pins in. Pieces are broken off and it's made them too short for reliable connection. I've seen this before. If the dies making the pins aren't properly formed or too aggressive in the forming process, metal fatigue results. One must chose the proper alloy base metal so the forming tool won't make it too brittle. A good designer accounts for the embrittlement during the forming process and makes it work to advantage. Starting with a too soft material that work hardens to proper function in the finished assembly.
My guess is that the component was used based on purchase price rather than to a quality spec with a mating cycle requirement.
All connectors have this spec stated or not. I've seen specs as low as 5 mating cycles before contact degradation. Mil spec components can have thousands of mating cycles. But, such parts usually cost more.
When your purchase decision is based solely on lowest cost (cheap), you can usually expect to have a cheap product.
Of course, an engineer can track down the source to validate connector durability. But, for a one-off repair, Note the power handling requirements. It "looks" like a molex connector pair would serve well for this application. But Hobby shops that sell electric components for RC car or airplane, make some pretty stout connectors, EC-3 or EC-5s. Even Deans connectors would last for years. Just make sure the male pins are dead when disconnected. I have Tamiya cars and trucks that have connectors for battery connection that take a prolonged number of mating cycles without degradation. Only an ESC short seems to take them out (in a rather spectacular way)! Anyway, it was industry standard and are pretty readily available. Almost certainly will give you the reliability you seek.
Cheers,
