 When the Quiet Zone car was introduced in each set, this was marked on the exterior of the doors by a magenta and white sticker.On 19 April 2004, the unusually large rate of increase in atmospheric pressure led to an airlock and failure of hydraulic pressure on eight of the Class 357 trains which caused their computer's software to lower their pantographs and so be unable to collect power from the overhead lines, causing service disruption.After their technical problems were sorted out, they have since been the most reliable fleet of EMUs in the United Kingdom, winning Best Modern Era EMU at the Golden Spanners Awards from 2005 to 2007, for an average annual miles per casualty (MPC) figure of 43,180 in 2005, 37,391 in 2006, and 45,459 in 2007 (defined as the number of miles a train runs before a defect develops causing 5 minutes or longer delay).