Precision 7760 bluescreen - UHD problem.

7760 bluescreened while unattended and in Win 10 lock screen. No apps were open. 

BlueScreen code 116 pointed to a video problem. When onboard diag (F12) was ran, it reported nothing wrong with the video system (it's pretty basic and dumbed down), when online diagnostics (https://www.dell.com/support/home) was run, it reported " Warning - Dell PC Diagnostics has encountered an unexpected result", and no specifics, which is completely worthless as a diagnostic tool.

How is further diagnosis information extracted to find the cause of the problem?