| Possible Causes | Solutions |
| Too much varnish lay down | Decrease quantity |
| Varnish viscosity is too high | Decrease viscosity, 1:1 of ethanol and water |
| The temperature of the heating section is low | Rise the temperature or decrease machine speed |
| The PH value of varnish is too high | PH value should be at 8 to 9 |
| Local excessive varnish consumption | Adjust gap |
