The left and right rear wheels are different. Look at the picture.

See if the wheel is splayed from the back, that is to say, the upper end is inclined inward. If so, please carry out the maintenance of the rear axle quickly and check whether the needle bearing and barrel are short of oil and worn. If the wheel is straight, see if both sides are equally low. Measure the ground clearance between the ground and the rear wheel frame with a ruler. Does the shock absorber leak oil? If you feel poor permeability, you can adjust the torque.