If you are having trouble with one or both sides of your robot walking, please check the assembly of both "Leg #1" and "Leg #2" (pp.12-13)
Refer to examples below for correct leg assembly:
Make sure screws (circled in red below) are completely tightened so leg assembly does not loosen during operation.
Make sure the second P1 is inserted as shown on step 12
Make sure P12 is inserted securely. The peace should be firmly inserted so it is not easy to remove, but not too tight that the P1 pinion cannot spin freely. Make sure that P1 can turn freely.
If one side of the gearbox is not working, then make sure the gearbox is completely sealed with the screws securely tightened so there is no space showing between the A5 and A6 sides of the gearbox. Please also make sure the motor wires are not in the way of the gearbox fully closing.
If your Robot is running in circles.
Make sure that the robots arms are not in front of the infrared sensors located under the robots eyes.