WASHINGTON—Production at U.S. factories increased moderately in January as motor vehicle output fell for a second straight month amid an ongoing global shortage of semiconductors. Manufacturing output gained 0.2 percent last month after dipping 0.1 percent in December, the Federal Reserve said on Wednesday. Economists polled by Reuters had forecast factory production rebounding 0.3 percent. Output increased 2.5 percent compared to January 2021. Shortages of materials have also afflicted other segments of manufacturing, in addition to the motor vehicle industry. Spending shifted towards goods from services during the COVID-19 pandemic, but manufacturers have struggled to cope amid an acute shortage of workers on factory floors and other places along the supply chain, caused by the coronavirus. Manufacturing, which accounts for 11.9 percent of the U.S. economy, remains supported by still-lean inventories at businesses as demand for goods remains strong. Production at auto plants fell 0.9 percent last month after slipping …