I have this same machine and I have always used Isocord embroidery thread and never had problems with breakage. my machine started doing this a few weeks ago. break and shred. i took it into the shop and they told me it was sewing fine, of course they didn't have it on a frame. after ripping out 9 rows that had skipped stitches broke threads I decided it must be my Sure Stitch regulator so today i unpluged the cords going to the box and left it off about 20 seconds pluged it back in and sewed 4 rows and it never broke a thread or skipped any stitches. sometime it would break three or four times before i got one row.I was ready to give up on my Isacord thread as it is very fine and i thought it was the problem was my thread. wish i had reset my Sure stitch before i had ripped out so many rows.