Hi Digitalp2k,
In yourprojectfolder/Config/DefaultEngine.ini try adding/changing
[/Script/WindowsTargetPlatform.WindowsTargetSettings]
DefaultGraphicsRHI=DefaultGraphicsRHI_DX12
to DX11
BUT FIRST
Try just disabling instanced stereo in that ini file
vr.InstancedStereo=False
ALSO
Consider trying the 5.1 preview. (And let me know if you are still crashing or if it is resolved)