Wobbles During Flight
As soon as you take off it begins to wobble and progressively gets worse until it crashes.
The gyro most likely broke when it fell or the top rotors hit an object. Follow the Syma S107 Gyro Replacement Guide to solve the issue.
Rotates While Hovering
Hovers fine and you've reached the limit of adjustment on your controller but it still rotates left or right without touching the controller.
Bad Rotor Motor
One of the main rotor motors is weak or going bad causing the two main rotors to rotate at different speeds. See the Syma S107 Rotor Motor Replacement guide to replace the motor.
Won't Turn On
You've charged your S107, but when you turn it on no lights flash.
The battery could be dead from quickly charging and discharging too many times. Also, the battery wires may have been broken or disconnected for the circuit board. Follow the Syma S107 Battery Replacement guide to install a new one or reconnect the wires.
Bad Circuit Board
The circuit board may have been shorted or faulty from the supplier. Follow the Syma S107 Circuit Board Replacement Guide to install a new one.