Not normal at all, not for Zippy's, or any other brand name switch. What is likely is that these aren't true Zippy switches, rather some very cheaply made parts from a Chinese factory which bear the high tech Taiwanese company's name, maybe with their permission, but probably not.
If it's a cruddy beige, or two-tone plastic, with one of those being the cruddy beige, then it's probably a knock-off. I've seen plenty of the standard Zippy microswitches, and the ones straight from the factory have been either a nice white, or solid black, but not that beige color. Also, I just looked and found online supposed Zippy parts being sold out of China with that appearance, and they had a model number which doesn't appear in the Zippy catalog.
That being said, put a drop of silicone spray on the actuator. It won't change the dynamic of a crappy switch, but it might fix the sticking.
RandyT