If the arms that hold the ratchet shaft are misaligned or binding the shaft in any way, the relay will stick. You can twist the shaft carefully with a flat blade screwdriver in the proper direction. Try removing the load that the cam wheel has by lifting the contacts away, as suggested earlier. The relay has to be adjusted precisely, but it will hold the adjustment for years. Another source of drag wiper arm(s). Ensure that the pcb is smooth. I put a tiny amount of light grease on it.