I would try again before making a decision to purchase the fonts.
What you are experiencing (loops under the stitching) is referred to as "bird nesting".
(1) Remove the needle and bobbin.
(2) Clean away any lint or thread snips that may have accumulated in and around the bobbin case.
(3) If you changed the tension, put it back to the factory recommended setting.
(4) Replace the bobbin, being sure the thread is feeding off the spool in the correct direction and through the guides.
(5) Replace the needle with a new one.
(6) Re-thread the EM with the presser foot up.
(7) Use cut-away stabilizer on knits.
(8) Do a test stitching on a scrap of like fabric and stabilizer.
If you are still having the problem, then a font may be the answer.
Pattiann