Performance Modeling Club of NW Washington

I have been airbrushing a body with House of Kolor paint and am having issues.  I primed the body using my airbrush and HOK primer.  It looked great.  I was excited!   Cleaned the air brush.  I then started to spray the color coat.  Every so often It would intermittently sputter a large glob of paint.  It would spray fine then a glob would come out.  Does anyone have a clue  what would have caused that?