If your vehicle is showing window rolls down crooked or falls down into the door panel, here are the most likely causes and the parts you'll need to fix each one.
The window regulator uses metal cables and plastic guide clips to raise and lower the glass. Over time, the plastic clips become brittle and snap, or the cables fray and break, causing the window to lose support and fall into the door.
The window glass is held to the regulator by clamps or bolts. If these were not tightened properly during a recent repair, or if they loosen from vibration, the glass can slip out of the regulator track and tilt sideways.
The rubber weatherstripping tracks that guide the sides of the window can become dry, torn, or bunched up. This causes the glass to bind on one side while the regulator pulls down on the other, resulting in a crooked window.
The internal plastic gears inside the window motor can strip out. While this usually results in a grinding noise without movement, a complete gear failure can remove the holding tension on the regulator, allowing the window to drop.