Unreal Engine 4.22 Preview

When I launch UE4.22 preview 2 with -dx12, the engine freezes after a few seconds, without crash warning window.

I’m running a RTX 2080 Max-Q Design on the Razer 15, with the 418.91 drivers.
I have Win10 1809,
In a blank new project I have enabled both the enabled Support Compute Skin Cache and Raytracing in the project settings
I have tried a clean re-install of both the Nvidia drivers and UE4.22 p2.
I have also tried to reset all settings to default in the Nvidia control panel’s 3D settings.
I’m not using any fancy software or anti-virus
Once it’s frozen, in the task manager the UE4 app appears and disappears even when the list is pinned by name : |

any ideas or advice?

Thanks for your help

[EDIT 2] After having a closer look at the GPU activity monitor I can see that UE4editor.exe is running with the 2080 Max Q GPU. For some reason, when I run the editor with the -dx12 arg, with the laptop screen as primary or/ only screen, it freezes after a few seconds. It seems to happen faster when opening the raytracing dropdown menu. It systematically freezes once Pathtracing kicks in or when I fire a raytracing Cvar. But when I run it on a secondary screen as primary / sole screen, everything seems to be in order.

[EDIT 3] I have reported the bug: Case # 00099889