Also ensure that you are plugging your Joulescope directly into a USB port on the host computer. Avoid using USB hubs, docks, and adapters. If you must use a hub, ensure that it is a powered hub with sufficient power for all connected devices.
For your long-term test, you should plan on using a dedicated computer that you prepare. You need to disable power management and anything that can reboot the computer or degrade performance. I recommended disconnecting networking entirely.