Flickering problem on Secondary Window on Multi GPU System


I’m the main developer of Black Ink a drawing software using DirectX to render his UI.
Some user report some weird flickering on secondary Window of the Application.
This issue isn’t reproducible here ( won’t dont have system with 2 GPU ).
The issue only occurred when the NVidia GPU is selected as the rendering graphic card. when the user selected the Intel HD all is fine.

here 2 video showing the problem


Video captured on a Surface Book 2
GPU: GeForce GTX 1060 6Gb
Windows: 10 (1909 18363.752)

All swapchain are rendered with a SyncInterval of 1 ( which mean the the program wait the VSync ).

if anyone had a solution would be great.