When I got my Juki tl98Q 8 years ago it would sew a line on perfect stitches for about 8 inches and then make a long stitch. I wasn't machine savvy at that point and couldn't figure out what to do. I called the dealer who sold me the machine (he was 5 states away) and he said he had no idea why it was happening. I first turned the upper tension knob all the way up and then down to the bottom several times. Next I took the manual and rethreaded making sure the thread went between the two discs. I set the other tension all the way at the beginning and kept moving in tighter. I sewed and sewed and sewed! It finally worked it's kinks out. Recently it did the same thing on a quilt and I think I'm going to have to do the same thing again! I still can't figure out why it gets fussy.