Patterned cracking in the surface of the paint film resembling the regular scales of an alligator.
Application of an extremely hard, rigid coating, like an alkyd enamel, over a more flexible coating, like a latex primer.
Application of a top coat before the undercoat is dry. Natural aging of oil-based paints as temperatures fluctuate. The constant expansion and contraction results in a loss of paint film elasticity.
Old paint should be completely removed by scraping and sanding the surface; a heat gun can be used to speed work on large surfaces, but take care to avoid igniting paint or substrate. The surface should be primed with high quality latex or oil-based primer, then painted with a top quality exterior latex paint.
(image courtesy of The Rohm and Haas Paint Quality Institute)