Cabinet doors sag when a screw or hinge comes loose, when the hardware is damaged, or when the wood underneath the hinge is stripped or gouged by a loose screw. You need a screwdriver. (A helper makes it easier to hold the door in position while you work.)
Tighten Loose Mounting Screws
Open the cabinet door and look at the part of the hinge attached to the cabinet box. Two screws, located at the top and bottom of the hinge, mount the hinge to the cabinet. Turn these screws clockwise to make sure the door is secure.
One of the main causes of a dropped door is a loose hinge. Luckily, this is really easily solved! Over the years, screws will naturally work themselves loose. You'll probably notice that you've got a dropped door because of loose hinges if the door drags on the floor a little.
A highly effective way to fix a sagging door is to replace one of the top-hinge screws with a 3-inch long screw. This serves not only to pull the hinge closer to the door jamb, but also it draws the entire door frame closer to the underlying stud.
Loose hinges can cause a door to drop
Over the years, screws will naturally work themselves loose. You'll probably notice that your dropped door issue is because of loose hinges if your door drags along the floor slightly. This is easy to fix, and all you need to do is tighten the screws using a screwdriver.
You may want to cut some type of prop stick that can be wedged between the counter and the bottom of the cabinet to help raise it upward so that it is tight to the ceiling. If the cabinet is recessed back more than two inches from the soffit's edge, you will have to find a wall stud to fasten the cabinet to.
To overcome Racking, pull the drawer out all the way, thus extending the slide members back into alignment. Then push the drawer back in. You may have to do this two or three times to ensure the slide members are fully in sync.
When the weather gets chillier, the wooden fibres which make up your door will begin to contract. When things get warmer again, those same fibres will expand. After a while, this cycle of expansion and contraction will cause a door to become the wrong size and shape for its frame.