I have a client that bought 9 machines from us, 6 520's and 3 500ci's. All 3 500ci's are giving us problems with jam codes but we have no problems with the 500's. The jams that we are getting are 31, 45 and 51. Most jams seem to Z fold at the registration or just get caught in the fuser. We have replaced the paper on all of these machines but we are still having the same problem. We have also tried the latest firmware and have adjusted sim 51 (Seat Paper Loop Amount). These are machines that are not even a month old and they've done it from day 1. If anyone has had any problems like this we could use your help. Thank you.