Just in case it's useful, my SurfaceBook 2 stopped charging which was always done via the Surface Dock. I have no idea why this might be, but flashing the firmware (on the Surface Dock) to the latest version resolved the issue and it started charging again.
HOWEVER, a side-effect is that any USB headset that is connected whist the laptop is docked with have intermittent microphone issues. Actual sound playback is fine.