The actual breakage was probablly caused by physical force but I strongly suspect the plastic case was weakened by hot running and/or was simply not of an appropriate standard in the first place.
The wire connected to the live pin looks worryingly thin and the markings also leave a lot to be desired, the only approval markings are CE and CCC, the CE mark is misprinted and there does not appear to be any indication of a manufacturers name.
But that's is normal operating current. It's adequacy under fault conditions depends on what (if anything other than the circuit's OPD!) is protecting it, doesn't it?
Also inform your local trading standards office. Dangerous items like this need to be removed from sale but the manufactures and others making a profit from them will not voluntarily stop selling them. Enforcement is needed.
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