Common faults in curtain coating include: 1. Unstable or broken liquid curtain 2. Uneven coating thickness 3. Coating sagging or running 4. Air bubbles in the coating 5. Pinholes or fish-eyes (craters) in the coating 6. Particles or impurities on the coating surface 7. Coating waste or low recovery efficiency 8. "Orange peel" effect on the coating surface 9. Poor coating quality at workpiece edges 10. Malfunctions in the coating circulation system