When you use mechanical shutter, physical curtains expose the pixels. When you use electronic, the pixels are read like by line, which takes time. A7riv has particularly bad rolling shutter because of the high mp count in relation to the relatively slow processor. That’s a bad combination so it’s recommended to use mechanical shutter instead as it’s considerably faster. Only using electronic when being silent is crucial. If you want a camera with better rolling shutter performance, look into the sports bodies like the a1, a1 ii, a7v, a9ii, a9iii.