+ The area around the hole in the needle plate is damaged.
+ The needle hits/touches the needle plate.
+ The presser foot is set too high and not correctly positioned. The needle hits/touches the presser foot.
+ The area around the embroidery foot hole is damaged.
+ Sliding surface on hook race is not smooth. There are scratches or burrs on it.
+ The hook is not correctly installed.
+ The hook stopper is not correctly installed, the hook is making a complete rotation.
+ The needle and the hook are not correctly passing each other.
+ There is backlash play (forward/backward) in the needle bar case.