There’s no magic fix that works on every computer regardless of hardware (especially g-card) and what game you want to play, on the other hand it might just need a reboot because you are half-way through updating your direct X 12… you haven’t given us ANY info at all mate.
As was mentioned, you system information may be important. But my system, 2 GTX 980s are working but crashing and taking the entire system when playing Borderlands2. I am not getting a dump file, but the system has to be restarted to get back to the desktop. The freezes occur usually after 10-15 minutes, but seem to have no common symptoms. It is like the system gets tired and needs to quit.
I suppose I am lucky that my graphics cards even work in this build, since they did not in the previous build. I have gone back to 8.1 on my gaming system and will wait to see if the next build improves the situation. One of the big issues with Windows 10 seems to be in the Graphics area..... maybe a future build will help.
I am not certain DX 12 is relative in these situations since nothing I have runs using DX 12 even though the video cards are capable. DXdiag does show DX 12, but the Nvidia drivers are using DX 11. I can't even find a benchmark or demo I can use to check DX 12...