Multiple T470s unresponsive when docked

We have multiple T470s ThinkPad's which when connected to the ultra dock 40A2, will randomly become unresponsive to input via Bluetooth or USB. The laptops all run with

their displays closed and opening the display or undocking the computer allows functionality to return. When the issue happens, the external display remains powered on and the time is changing which indicates that the ThinkPad has not fully frozen. Plugging in a USB mouse to either the ThinkPad or the dock results in no power light or activity, however, if the mouse is connected directly and the computer is removed from the dock, the mouse powers on and works as expected.

The laptops have all been fully updated with drivers via the Lenovo System Update app and they are also running Windows 10 1803 with all available updates installed. As far as I can tell, only one firmware update for the docks is available (2.33.000) which has been applied with no change

The issue can affect the same user every 10-20 minutes one day (persisting after restarts etc) and then the ThinkPad works fine the day after. No errors or alerts are shown in Windows event viewer to indicate an issue has occurred

Thank you for your time

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