Switching Graphics API to D3D12 in the Blacksmith scene of the Environments demo project causes the editor to crash. Switching API in another scene and then opening the Blacksmith scene does not cause a crash. Once Blacksmith scene has been opened in D3D12 switching back to D3D12 in that scene no longer causes the crash.

*NOTE : Scene visuals have been massively stripped down (assets removed from project) to reduce size of repro project. However, behaviour is consistent with the full version of this scene and project. (Can test from "X4_VOLUND/trunk/environments" SVN)

Repro Steps:

1) Enable DX12 in editor (-allow-d3d12 command line argument)
2) Open attached project and scene "Blacksmith"
3) Change Graphics API to DX12 and witness crash (editor.log)
4) Re-open editor with DX12 disabled
5) Re-open attached project and scene "Blacksmith"
6) Change Graphics API to DX11 and close
7) Enable DX12 in editor (-allow-d3d12 command line argument)
8) Open attached project, create new scene, save and then change Graphics API to DX12 (witness change works)
9) Now open Blacksmith scene and witness that it works

Now you can open the scene in a non-DX12 enabled editor to change back to DX11 (another bug crashes editor changing out of DX12 otherwise) then open back up in DX12 editor and switch to DX12 in Blacksmith scene. Notice how this now works.

Crash in "D3D12SerializeRootSignature"

Regression from V5.3.0f4