18aa367c_ooting_Sewing_Machine_Problems__Symptom
[Root Cause] Dust has accumulated in feed dogs. Lint is in hook. Thread caught in shuttle. [Corrective Action] Clean machine. Clean machine. Disassemble machine and clean shuttle. [Symptom] 
Loud noise is heard. Knocking noise, machine jammed.
Troubleshooting Sewing Machine Problems
Symptom