How to fix RHI/D3D11 crash?

if i remove ‘DefaultGraphicsRHI=DefaultGraphicsRHI_DX12’ from the Config folders DefaultEngine.ini of any 4.25 project of mine that wont start it loads without problem.

if i re-enable [actually the ‘raytrace’ flag is still one under project settings when i load the project] and select Direct X12 under the RHI [also in project settings] and restart the Editor, bam!..again the editor does not finish loading the project and i get the above assertion failure…

if i open a non rtx project , no problem there.

I’ve uninstalled/re-installed/verified 4.25.4 tried numerous studio drivers including the latest and previous ones too [alwasy using DDU in safe mode and preventing windows from installing what it wants by unplugging the net] but nothing helps with this.

Can anyone offer any help…this is driving me crazy now for days and Im out of ideas…
thanks in advance.

Assertion failed: Size > 0 [File:D:/Build/++UE4/Sync/Engine/Source/Runtime/D3D12RHI/Private/D3D12Buffer.cpp] [Line: 93]

UE4Editor_Core
UE4Editor_Core
UE4Editor_D3D12RHI
UE4Editor_D3D12RHI
UE4Editor_D3D12RHI
UE4Editor_D3D12RHI
UE4Editor_D3D12RHI
UE4Editor_RenderCore
UE4Editor_RenderCore
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_CoreUObject
UE4Editor_Engine
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_Engine
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor_CoreUObject
UE4Editor
UE4Editor
UE4Editor
UE4Editor
UE4Editor
kernel32
ntdll