• The paint has not been stirred sufficiently beforehand
• Paint coat not applied in sufficient thickness
• Unevenly sprayed
• Too much thinner added
• Flash off times ignored
  

Prevention

• Stir the mixing colors well before use
• Apply the recommended number of coats or spray until covered
• Use the right spraying techniques
• Readjust viscosity
• Allow sufficient flash off time
  

Remedies

• Abrade the paint finish and re-spray