Polish trains have been found to lock up when serviced in third-party workshops, allegedly due to a backdoor or hardcoded checks. The issue was discovered by a group of hackers who were contacted by a train operator to investigate the problem. The trains' manufacturer, Newag, had claimed that the trains became unresponsive due to malpractice at the train repair shop. The discovery has sparked discussions about potential fraud, sabotage, and extortion.