Slowly remove the metallic clamps from the plastic body to free the plastic case, holding the rotating mechanism .(If possible remover the metallic case fully from underneath the board, if it is not soldered)

Pull back or bend the plastic case a little bit for easy insertion of spring

Place a small coil spring on the extreme end of the small metallic plate holding the rotating mechanism against the plastic body

Pull the other end of the coil and place it on the other end where the scroll wheel is inserted

This will ensure that the small metallic plate and rotating mechanism are not loose thereby not causing a jumpy scroll wheel