China’s adoption of unmanned convenience stores, where customers use their mobile phones to scan barcodes and pay for items themselves, has hit a glitch – high summer heat has melted some of the snacks inside. Two of the stores operating in Shanghai were forced to close temporarily as a result of poor air conditioning. One is operated by technology start-up BingoBox, and opened last month near the China headquarters of French retailer Auchan, which supplies the hundreds of products offered. Some customers had complained that cakes were misshapen and chocolate had melted. A company employee said the store would reopen soon after “improvements”. BingoBox opened the Shanghai store after months of testing the system in its home province of Guangdong. The second one followed just a week later, also in Shanghai, but in partnership with Taiwanese franchise owner RT-Mart. It, too, was shut on Monday while workers installed an air conditioner. The business model relies on a mixture of mobile phone technology, facial recognition software, and a smattering of personal accountability. Potential customers must first register with the company using their real identity. Once approved, they can enter by using their mobile phone camera to scan a QR code at the door, sending the data over WeChat. Inside, they choose the items they want, scan them at the register and pay either through WeChat or Alipay. A camera scans customers on the way out and anyone carrying items they don not pay for is recorded in a company database. Although the store operates without staff, customers can contact an assistant through a video screen. There are now altogether eight outlets in Shanghai and Guangdong, offering snacks and daily necessities at prices 5 per cent lower than traditional convenience stores, China National Radio quoted Wang Ying, BingoBox’s vice-president of marketing, as saying. Alibaba, which owns the South China Morning Post , unveiled its unmanned Tao Cafe self-service store in Hangzhou, Zhejiang province, on Saturday, while retail giant Wahaha has pledged to open 100,000 staffless convenience stores with artificial intelligence within the next three years. Pan Fei, from RT-Mart’s business development department, said the closure was due to problems with heat. “We will see how people receive this and decide later if we will introduce more,” he said. However, some residents are still sceptical about whether the new wave of snack stores will be embraced. “This kind of business model should rely on the personal credibility system, which is still immature in China. So it’s very hard to prevent theft,” one internet user commented on Weibo.