There are many reasons, mainly due to the poor cooperation between the lock and the needle! In the madness of normal sewing, at this time, you put the sewing machine head down, slowly turn the pulley, and then pay attention to the coordination of the three needles, the twist lock, the thread ring, and the thread. I know why.
Adjustment method:
1. Adjust the height of the needle bar.
2. Adjust the distance between the needle and the tip of the twist lock
