Hello, @joyenjoy . . . I have moved your new topic to this thread for issues with legs and feet on EMO which leg shaking is one of those problems.
Please try first cleaning the foot sensors here.
If this is not successful, you will need to contact Support at service@living.ai as his leg servos may need either recalibration or repair. Be sure to include a link to a video showing the problem and his four digit alphanumeric I.D. when he signs into the app.
Let us know how it goes.