I'm the original poster to this now (very large) thread.
By way of update, we have three Surface Dock 2s, and two Surface Dock 1s.
Some 8 months later, the problem remains for the Dock 2s. They are all complete lemons. I have had several replaced. They simply do not work (originals or replacements).
It is a lottery each day when we start our tablets as to whose monitors will work and whose will not. Sometimes they do, sometimes they do not.
I have tried each and every thing in this thread and nothing fixes it. I've updated the firmware so many times that the word "firmware" has lost all meaning to me.
The Dock 1 - completely fine. No issues whatsoever.
To say I'm disappointed in the Dock 2 would be a gross understatement. Why on earth would you put out a new product that is so much worse than the old one?