I am intrigued some people believe it could be the dock itself. I have a SB1, SB2, and SB3, Two dock v1, and a dock 2. The issue happens only with the SB3, and with all docks. Swap in SB2 or SB1, they have never had any issues with any docks.
Beyond this, a work colleage has an SB2 and SB3 and Dock v1 and dock 2. He never had any troubles with any of that till this week. Suddenly, no monitprs on the docks, and no usb on the docks. Laptop usb is ok.
The connector could be a possible cause. Maybe the connector just does not connect correctly. The manufacturing issue could be sometimes on the plug side and sometimes on the socket end. That would explain some resolving it with new dock, and some with new (or older) SB.