Many chinese power supplies, if the neutral becomes disconnected but the live remains, such as in the case of a severed cable or supply grid fault, the output side of the supply can rise to supply potential, giving 240v where only 12v is supposed to go. Fire and electrocution is a very real possibility, especially since so many chinese products come with no fuse protection and undersized wiring.
about 2 thirds of the ones we investigated had underrated components, inadequate primary-secondary isolation, single component failures can cause either supply potential at output terminals or the device to catch fire. The plastic housings are of poor construction, a small knock can smash them leaving bare live unfused connections. Thousands of other examples but i don't have all day to list them. There is no regulation to stop these parasitic companies putting out dangerous equipment with falsified specs, in the uk, at least there traditionally has been a guaranteed minimum standard of quality and safety so people who buy on price alone still get a reasonably safe product that does roughly what it says on the box(except maybe british cars, maybe communist manufacture is the common denominator in **** quality?), dealing with chinese companies, there are no such safeguards, anything goes and there are a lot of scum getting away with outright theft. Until something is done about that side of things even good chinese products will be disregarded as chinktat unfortunately.