Thank you tdf2001 for posting a procedure that works for your configuration. I've given it a try with my two 4K monitors and unfortunately, at step #6, the "panic" state that I am familiar with sets in.
In this state, all of the monitors slowly cycle on and off repeatedly. The first 4K will briefly show a desktop and then turn off and repeat, the internal display will do the same. The second 4K will cycle between indicating "No signal" and "Sleep imminent." (To be clear, the second 4K monitors never shows a glimpse of the Windows desktop). Meanwhile, the USB devices are power cycled as well, and the USB detach and attach sound effects are repeatedly played.
It's as if the dock is attempting to power up the second 4K monitor, encountering an exception, and "rebooting" itself (the dock), causing all attached devices to be re-recognized. Which then re-recognizes the second 4K monitor, which it attempts to power up again, and the process repeats.