Wall Street Journal: A key component of the Apple Watch made by one of two suppliers was found to be defective, prompting Apple to limit the availability of the highly anticipated new product. The part involved is the so-called taptic engine, designed by Apple to produce the sensation of being tapped on the wrist. After production began in February, reliability testing revealed that some taptic engines started to break down over time. Apple doesn’t plan a recall, because there is no indication that the company shipped any watches with the defective part.