There are many different ways that electronics can fail. If the electronics experience a significant amount of shock or vibration, that can cause connections to weaken or break. Some components age and fail, such as electrolytic capacitors. Some components are sensitive to overheating, overvoltage, or just in general having the power be out of spec. Solder (especially lead free solder) can develop tin whiskers that cause short circuits. And there are numberous other ways.
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