You may have a burr on your cutting edge, or it has slipped out of position somewhere. My machine did this when I knocked out the timing, had to get a repairman to look at the thing -took him 2 seconds and no charge. Lucky me! I purchased a copy of a book that I have found an excellent resource - The Ultimate Serger Answer Guide by Naomi Baker, Gail Brown and Cindy Kacynski - it suggests a few things to try 1. Make sure the upper knife is in the correct cutting position 2. Check and reset the lower knife blade as it could be out of alignment 3. check and clean area of any lint or threads 4. look for nicks or shiny spots on the blades That is all it suggests....I would suggest asking for the book from a library should you wish to investigate more. Good luck let us know how you make out. Another thought - sometimes it isn't how long we have had the machine but how much we have used it and exactly what fabrics we have been working with can dull the blades.