Hello, There is an issue with SD-509 booklet making unit and it will be fixed only if there were ~10 thousands complaints. The main issue is with a unit that aligns the paper when it falls into "saddle" before stitching. It is made of very thin metal and if this finisher is used with thicker paper, it deforms (there is a big speed of paper). So I would like to ask everybody to complain about it if you (or your known persons) own this modification machine. This unit is quite popular and is used with C452 and other models. Thank you in advance. P. S. I will add photo ASAP when machine stops working