A dishwasher door that suddenly falls open or slams to the floor usually has a problem with its door suspension or linkage system.
Many dishwashers use a balance link, which includes a cord, pulley, and spring to keep constant tension on the door. If the cord breaks or separates from the connector, the door loses that tension and becomes heavy, causing it to fall open quickly.
Some dishwasher models use a friction pad instead. If the pad wears out or comes loose, the door can free-fall because there is not enough resistance to hold it in position.
Depending on the model, the fix may involve replacing the balance link, cord, pulley, spring, or friction pad.