It has been said many times on this board, but maybe it needs to be repeated.
Walking feet are not designed to be used while sewing backwards. The walking foot has only one direction, forward. The up and down motion of the needle moves the walking foot and it has no way to determine the direction you are sewing. Therefore, it always moves forward even if the lower feed dogs are going in reverse. Continual use, while sewing in reverse, will eventually break your walking foot.