If it is anything like the shutter on the CLS2000, I believe the shutter reversing is controlled 'mechanically' with a relay and contact switches on the eccentric shaft that controls the shutter. That is to say, the rotation of that shaft is not 'computer' or 'microprocessor' controlled. This means that, if you are lucky, you just have a faulty contact switch or bad relay. My shutter was not working because the prior owner blew a resistor. I replaced the resistor and it works fine.