I had a similar problem with a different brand and actually blamed the brand for it. In retrospect, I may have just tightened down the face-plate or switch assembly too much and bent it enough to interfere with the relay's action. Whatever the case, I put those exact switches in to replace the others and they've worked flawlessly ever since. Also, with fans, it's a good idea to check amperage required. Some fans draw quite a bit and the switch may not have enough to do it (or do it safely). That's one reason my bathroom fan is still manual. (The other is that it has two switches, mounted vertically in one space. )