You have a new topstitch needle in there already, great. Do you have the proper sized needle for your thread? I really like Dr. Bob from Superior Threads and this 2 part presentation on needles / enjoy:
https://www.youtube.com/watch?v=4U48srIlnWg
https://www.youtube.com/watch?v=magTIhmFVgw
Consider thread tension too. Dr. Bob on thread tension:
https://www.youtube.com/watch?v=9hSMw0jTeeQ