https://medium.com/@GadgetHax/everything-you-should-know-about-rolling-shutter-on-your-phones-camera-6ea6f51b6c98

Smartphone videos get better and better each year. Seven or eight years ago, who would have thought iPhone and Android phones could support 4K video recording. Some phones can even shoot slow-motion at 960 fps. But no matter the resolution or frame rate, a phone’s rolling shutter can make quick movements in front of the camera appear wobbly, distorted, or with artifacts.

Depending on what you’re going for, a twisted look for fast-moving objects being recorded may be the effect you want. However, most of the time it’s just an unintended effect caused by the CMOS camera sensor built into your smartphone. Rippled. Warped. Distorted. Wobbly. Twisted. Slanted. Bent. Skewed. Stretched. Bouncing. Deformed. Jello effect. Light flickering. These are all things that can happen to your footage with a smartphone camera.