RE: Dell TB15 Desktop Dock - Step-by-step driver/firmware/BIOS installation instructions for XPS, Latitude and Precision notebooks
XPS 15 9550 & TB15 here.
Mine seems to be (mostly) stable with audio, Ethernet, keyboard, mouse and two external HDDs. What trips my TB15 up is when I connect to an external display, first with DP, then with a brand new mDP cable. Disconnects and hangs after that.