This can be caused by radio interference. This can be diagnosed by temporarily wrapping the radio or gyro in aluminum foil to see if the glitching stops. If the glitching stops, then this component is probably too close to the motor and/or ESC and should be moved to a different location.
The radio crystal may have been damaged in a previous crash. Try replacing the crystal to see if the symptoms disappear.
For brushed motors: the commmutator may be dirty. See section on maintenance.
Pinion meshing may be too tight. The pinion should not be firmly fitted against the main gear. The motor pinion should be able to wiggle just a tiny bit without turning the main gear.
Motor pinion may be slipping on motor shaft. If your motor pinion uses a setscrew, then your motor should have a flat spot on the motor shaft so the setscrew will not slip on the motor shaft.
If the motor shaft has no flat spot for the setscrew to bite, then you should make one with a Dremel and a diamond cylinder point bit (#7123).
For the Piccolo using the stock motor (G280 or G310)and the plastic motor pinions, it may be necessary to glue the plastic pinion onto the motor shaft to prevent it from slipping.
Woodies may be trashed:
Most larger wooden blades are made of a hardwood leading edge and a balsa trailing edge all shrinkwrapped together.
On hard crashes, the balsa part can be severely damaged but the blade looks fine due to the shrinkwrap holding the blade together.
If you look closely you may be able to see the breaks in the balsa. If you can see this, then the blade should be replaced.
If using a brushed motor, move the receiver and gyro farther away from the brushed motor and servos
If using a brushless motor, move the receiver and gyro further away from the brushed motor controller
Check all bearings on rotating parts. Bad bearings rotating at high speed can cause radio frequency interference.
This is normal. The helicopter will tilt slightly due to the thrust of the tail rotor.
Your headspeed may be too low and you may be compensating for this by using more main motor pitch which makes the heli motor bog down and the heli unstable.
Your rotor head may not be firmly attached to the main rotor shaft. This usually occurs when the hole in the rotor head is reamed out after multiple hard crashes. If the rotor head is not fitting snugly on the main rotor shaft, it should be replaced. This problem is seen on MS Hornets. because the E044 pivot support is fragile.
On a CP Piccolo, this is usually caused by a broken pitch arm base (68211). Visually inspect the two thin "legs" which are between the arms and the tube. One of the legs may have broken.
The feathering shaft may be bent. Disassemble the head and put the feathering shaft in a drill and spin it to check if the shaft is bent.
Cyclic servos wiggle around without joystick input when motor is running at or near hovering throttle
This could be radio interference. Make sure your motor leads are short and routed away from the receiver.
With a brushed motor, the motor brushes may be worn or the commutator may be dirty which causes radio interference.
Check your brushes and make sure they are in good condition and check the condition of the commutator.