Ok so it looks like I’ve got it working again, although I’ll have to redo all my preferences probably, or import them from my desktop setup.
Just in case anybody else comes across the same issue I basically uninstalled Dorico then deleted any related folders in the following locations (Windows 10):
C:\Program Files\Steinberg\Dorico 2
C:\Users<username\AppData\Roaming\Steinberg\Dorico 2
C:\Users<username>\AppData\Roaming\Steinberg\VSTAudioEngine2_64
I also cleaned up the registry a bit.
The video import is now running perfectly for me. 