Wheel peddling or spinning the left or right rear wheels there is a clicking sound like something is skipping. It comes from the right rear wheel area. When spinning the left rear wheel the right rear wheel will also spin like positraction on a car. There are four screws in the axel but I don’t know what they are for. The manual does not give me any information about them. How do I fix the clicking noise?

While pedaling or spinning the left or right rear wheels there is a clicking sound like something is skipping. It comes from the right rear wheel area. When spinning the left rear wheel the right rear wheel will also spin like positraction on a car. There are four screws in the axle, but I don’t know what they are for. The manual does not give me any information about them. How do I fix the clicking noise?