I have the exact same issue.
I thought it was a problem with the dock, but same thing with a new one.
I've noticed that USB and network disconnects/reconnects when the surfacebook is heating.
Example :
Programs lounched :
- Outlook
- Google Chrome
- Sublime text
I launch Photoshop, the fans begins to speed up (I hear them clearly), and here begins the disconnect/reconnect.
After the photoshop startup, fans slow down, and the disconnect/reconnect stops...
I think it's a overheating problem with the surfacebook, who disconnects the dock connector, without any solution...
Following that, it's normal that disconnecting the dock and working directly on the surface resolves all problems...
We've been complaining about this since it launched a year and 5 months ago. Pretty clear at this point this is a design flaw in the power management hardware that cannot be fixed with a firmware update. Just have to use powered USB hubs instead of, or in addition to, the dock, or swap it out for a laptop that was tested properly before launch.