Taskbar comes to front when PoE loses focus

Hi,
I'm using PoE with DX11 in fullscreen mode (not windowed fullscreen). Also I'm using Mouse Without Borders (https://www.microsoft.com/en-us/garage/profiles/mouse-without-borders/) to share my mouse and keyboard with a second PC. When I move the mouse to my second PC, the taskbar comes to the front. PoE is still in fullscreen mode but the taskbar covers the bottom of the game. When moving the mouse back to my main PC, the taskbar stays in front. I need to click on PoE in the taskbar, to minimize it und click again to maximize the game. Then it's back on fullscreen and the taskbar is gone.
I need to do this every time, I move my mouse to the second PC. This can be very annoying as there are many reasons in PoE to use a second PC or screen (trade site, wiki, PoB, etc...).

This problem only occurs with DX11. With DX9, everything is fine and the taskbar does not appear, no matter how often I switch.
It seems to be a PoE problem, as I don't have this problem with other games running DX11.

OS is Windows 7, graphic card Nvidia GTX 1070 (latest drivers).