RE: Trouble with XPS 15 9550, USB-C/Thunderbolt 3, and external monitors
Pabster1192 - Are you running the XPS 13? The topic here is for the XPS 15 9550. As I understand the WB15 is only for the XPS 13. The solutions/driver updates I mention are for the XPS 15 with the TB15 dock.
Also everyone else, there are firmware updates for the thunderbolt controller that were released July 6th (today)