Mine also crashes using Direct Mode. I think it is due to having a laptop with a dual graphics card setup; an Nvidia Geforce GTX860M and Intel Integrated Graphics. The HDMI port that the Oculus DK2 is plugged into is on the Intel Integrated card.
When I run Unreal with the Integrated Graphics card selected, it doesn’t crash but has an unusably slow frame rate.
This appears to happen for other games and not just Unreal so maybe an Oculus runtime issue?
Running in extended mode, with the Nvidia Geforce selected, the Oculus works fine; I can tell the Nvidia card is definitely doing the processing (even though the HDMI port is on the Intel card) as the frame rates are much higher.