I also agree it is the stabilizer and noticed that you do not mention the total stitch count. (Floriani stabilizers have a sheet of paper inside the roll that give the stitch count - I don't know about other brands.) Each stabilizer has a "max" number of stitches it can hold before you need to float another piece underneath. If you are reaching the total stitch count for the stabilizer you are using, put another good sized piece of tear-off stabilizer under the design when you reach that point and see if it helps. Just another idea to try.