The Boeing-produced Starliner spacecraft on Friday left the International Space Station (ISS) and was heading back to Earth without a crew following numerous technical problems. The spacecraft undocked from the space outpost at 6:04 pm (2204 GMT), US space agency NASA confirmed, after three months in space. It was due to land at White Sands Space Harbor in the US state of New Mexico after a six-hour trip. US astronauts Barry Wilmore and Suni Williams, who travelled to the ISS with the Starliner in June, remained stranded in space following numerous technical problems with the craft. Their stay…