BEIJING—China’s factories slowed their output growth in April and retail sales significantly missed expectations as officials warned of new problems affecting the recovery in the world’s second-largest economy. While China’s exporters are enjoying strong demand, global supply chain bottlenecks and rising raw materials costs have weighed on production, cooling the blistering economic recovery from last year’s COVID-19 slump. Factory output grew 9.8 percent in April from a year ago, in line with forecasts but slower than the 14.1 percent surge in March, National Bureau of Statistics data showed on Monday. Retail sales, meanwhile, rose 17.7 percent, much weaker than a forecast 24.9 percent uptick and the 34.2 percent surge in March. NBS spokesman Fu Linghui said while China’s economy showed a steady improvement in April, new problems are also emerging, notably the rise in international commodity prices. “The foundations for the domestic economic recovery are not yet secure,” Fu told …