Downward "drooping" movement of the paint film immediately after application, resulting in an uneven coating.
Application of a heavy coat of paint.
Application in excessively humid and/or cool conditions.
Application of over-thinned paint.
Airless spraying with the gun too close to the substrate being painted.
If the paint is still wet, immediately brush out or re-roll to redistribute the excess evenly. If the paint has dried, sand, and reapply a new coat of top quality paint. Correct any unfavorable conditions: Do not thin the paint; avoid cool or humid conditions; sand glossy surfaces. Paint should be applied at its recommended spread rate; avoid "heaping on" the paint. Two coats of paint at the recommended spread rate are better than one heavy coat, which can also lead to sagging. Consider removing doors to paint them supported horizontally.