Good cabinets can last for generations, and that makes them a bargain. The best value usually is measured by weighing cost and life span. But in as little as a year, junky cabinets often begin to fall ...
Ensure that the hinges are installed correctly and securely fastened to both the cabinet doors and the cabinet sides. You can tighten them using a screwdriver by turning the mounting screws clockwise.
If your cabinet doors are warped, you probably have a lost cause on your hands. The internet may offer you many ideas for how to fix those warped doors, including laying a heavy object on top of them.