There have been a number of posts regarding replacing the USB cables provided by DJI with higher quality ones. I haven't had a problem with the out-of-the-box cables, but others apparently have.
Your tablet / phone may also be underpowered for the live video feed, or you may need to give the Pilot app more resources. I have an Nvidia Shield, and had a problem with laggy video (not jerkiness, though). With some research, I found the default power configuration was "conserve battery", which didn't enable the full power of the tablet. Using the APP tab under Settings => Shield Power Controls, I set the Pilot app to a Customer power configuration: enable all four cores, 100% processor frequency, turn off Frame Rate Limit, use Native resolution rendering and turn off optimizing system memory. I also set the Battery Saver mode to only come on when the battery is down to 15%: the default was 75%, which meant the tablet went into Battery Saver mode too quickly and the app performance suffered.