Comment 34 for bug 1994126

I have the same issue for my Thinkpad P53 and I don't have a dock. It definitely related to the usb-c.

case 1: If I connect my external monitor to usb-c port, it may panic on boot ( I say "may" because sometime it can last till I successfully login and run for a minute or so and then it hangs and I have to hard reboot by pressing power button for a few seconds)
case 2: After I switch my external monitor to HDMI, the issue never happen
case 3: If I connect my iphone to the usb-c port before reboot, it can also panic
case 4: I disconnected iphone then power up and it can successfully boot. Connect iphone to the usb-c after boot and it has no issue.