@melmac - Thanks again for your reply.
I've not run the setup each time. In fact this was only the second time I've gone through the Oculus setup from the beginning. I always redo the sensors through guardian though.
Q: Plug Docking station into a USB 3 port, One sensor and one headset into the docking station and the other sensor into the free USB 3 port.
A: Yep, tried this configuration as you mentioned (believe I'd done it before, but checked once again) with the headset USB going into the USB 3.0 of the docking station (HDMI plug still going into the laptop - nowhere else to go), along with a single sensor in the docking station USB 3.0 and the 2nd sensor in the remaining USB 3.0 of the laptop. Still the same, but thanks for helping.
Anyhow, spoke to ASUS this morning and they believe I have a hardware fault and have asked I send the laptop into them for assessment and repair. I've also asked that they test the laptop with an Oculus.
Will update when I hear more.
Thanks,
James