I hhd same problem when I started FMQ on my juki. After about a month I called the company that I bought from as there is no local juki rep. He asked if I was using a 16 or 18 needle. I said no 14. He sent me a 18 and it never happened again. I can't find many 18 but I have been using a 16 and my thread rarely breaks now unless the needle is dull. Try a 16.