China’s high-speed railways experienced 168 problems in July, according to an internal Ministry of Railways report, of which 106 related to the quality of rolling stock.

21st Century Business Herald reported that high-speed trains built by China North Locomotive and Rolling Stock, one of the nation’s two largest train makers, were found to have the most problems. The report said 86 malfunctions occurred in trains manufactured by the company’s Changchun and Tangshan units.

However other major manufacturers, including a Qingdao unit of China South Locomotive and Rolling Stock Corp and the joint venture Bombardier Sifang Power (Qingdao) Transportation, also had problems with their products.