1)The rotors/propellers of your drone are made to be sturdy and yet soft so as not to hurt people or cause damage to other objects. They are thus quite susceptible to bending out of shape after several bumps. Always check each of the rotors before a flight to make sure they are in perfect shape.
2)If you are flying your UAV indoors, you are almost guaranteed to lack GPS signal. It is therefore recommended to always fly in open areas away from tall buildings whenever you can.
3)Incorrectly-tuned compasses are one of the biggest causes of drone crashes. Drone compasses can become detuned from any magnetic and radio frequency (RF) source. Avoid keeping the UAV is too close to magnets such as those in car speakers during transportation as well as flying in an environment with high electromagnetic interference, such as close to high voltage power lines and cell phone towers.
4)This is another common cause of drone crashes and can happen at any time from your first flight to some months later, usually arising from loose cables and damaged ports. Make sure your cables are always well plugged in before flight and unplugged carefully after, to keep the ports in good shape.
5)When you lose control of your drone, as a pilot one of the quickest natural reactions would be to hit the Return to Home (RTH) button but it worth keeping in mind that most consumer drones can’t avoid obstacles. This means the UAV will simply trace a straight line to the home point even if there are trees or buildings or electricity poles in the way; this can easily result in a serious crash. You shouldn’t panic to press the RTH button every time you lose control of the UAV, stay calm and figure out a better move.
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How many GPS you had ?