For the record, this is an ongoing issue for me as well.
All the obvious checks (Windows updates, firmware updates, Dock updates) have been completed repeatedly (even obsessively) over the past several months in the hopes that an update would fix the issue. Nothing has changed. Yes, I even check for Surface
Dock firmware updates regularly via the Surface Dock Updater.
Surface Pro 4 i5/256gB, purchased directly from the Microsoft Store in Boston.
Also for the record, I've tried using the "Answer Desk" multiple times for other issues - every single time this has proven to be a complete waste of time. Not only was the answer desk of no technical help, and not only did they seem to not understand the
basics of the machine (which is a Microsoft device, so you'd think they'd know it), but every time they stated that they would follow up with me via email. They were very explicit in this point, stating that they would get back to me one way or the other.
I have never received a single reply from them, neither by email nor phone.