A faulty Chinese-made component of the Apple Watch has forced the Cupertino, California-based technology giant to limit the availability of the product, The Wall Street Journal reported.

The problem occurred with some parts – known as taptic engines because they produce the sensation of being tapped on the wrist – that were made by AAC Technologies Holdings Inc., a supplier based in the Chinese city of Shenzhen.

The defect was discovered in testing after the product began to be mass produced in February, sources familiar with the problem told the Journal.

No defects have been found in production of the same part by Nidec Corp., a company based in Japan, the daily said.

The sources said Apple will not recall Apple Watches that have already begun to be distributed at luxury boutiques or via Internet because there is no sign that units with that faulty component have reached consumers.

Due to the problem, Apple has decided to source nearly all taptic engine production from Nidec, although it may take time for the Japanese company to increase production of the component. EFE

Another issue causing difficulties with the Apple Watch was reported by Dan Simmons, technology reporter for the BBC:

Darker-coloured artwork and even changes in darker coloured skin types can fool the light sensors on the back of the watch […] the manufacturer has not solved the sensor problem.

In some cases,  ink saturation and certain patterns of tattoos located close to the wrist may interfere with sensors that detect heart rate. This issue is not limited to the Apple Watch, and it specifically interferes with fitness apps.