Jitter can have several causes, including:

1. The power supply voltage is insufficient. This is the most common reason. If the power supply voltage of the servo is insufficient, it may not work properly. It is recommended to use a step-down voltage stabilizing module to supply power separately and keep the voltage at around 5V.

2. The steering gear is damaged. Although uncommon, the servo itself may be defective, in which case the servo will need to be replaced.

3. Electromagnetic interference. Stepper motors or other devices that may cause interference may affect the normal operation of the steering gear. Keep power lines and control signal lines away from these devices, and try to add electromagnetic shielding measures.

4. Signal line interference. Make sure that the signal line of the servo is not interfered by other power lines or signal lines. You can try to use shielded wires or increase the cable distance.

5. Program logic issues. When the host computer button is pressed, ensure that the instructions sent to the robotic arm are correct and stable, and check the program logic to ensure there are no additional operations or unstable instructions.

6. Servo drive circuit problem. Check whether the servo drive circuit is connected correctly and ensure that the power supply, ground wire and signal wire are all well connected.

7. The power line and signal line are not grounded together. The signal line and power line of the servo should be grounded to ensure stable operation.

8. Use low-quality servos. Low-cost servos may themselves be of poor quality, causing jitter.