Rolling shutter

Most cameras expose an image one row of pixels at a time, top to bottom. The gap between the first row and the last is tiny, and anything crossing the frame quickly during that gap gets recorded in two slightly different places. Vertical lines lean and propeller blades bend. Handheld footage shot on a bumpy surface picks up a rubbery wobble.

Global shutter sensors read the whole frame at once and the problem disappears, though they stay rare and expensive. On the camera you already own, the fixes are slower pans, a tripod, fast movement kept away from the edge of frame, and a shooting mode with a quicker readout where your camera offers one.