When using ChangeDisplaySettingsExW to change the primary monitor resolution while a secondary monitor is present. It's possible that the monitor layout will change, e.g., from aligning horizontally to vertically. And then if we only restore the primary monitor resolution, the layout is not kept. Some games expect the monitor layout is kept and the tests prove it. For example, there is a chance that RiME will hang on KDE if you quickly get in and out of fullscreen mode multiple times.

The layout change is caused by calling ChangeDisplaySettings for a specific monitor. It happens in cases when moving the secondary monitor in one direction is closer than moving it to the original direction. For example, a primary 3840x2160 monitor and secondary 800x600 monitor on the right with the top side aligned horizontally. Now call ChangeDisplaySettings to set the primary monitor to 800x600. If the secondary monitor moves to the left. Then the offset is 3840-800=3040. However, if it moves upwards, it's -600. abs(-600) < abs(3040) so the secondary monitor end up on the top side of the primary monitor. You can test it on Windows as well. Finally restoring the primary monitor will keep the secondary monitor on the top side. Thus a layout change. I don't remember the exact reason why the layout change will solve the hang. If DXVK's DXGI can pass wine's DXGI tests, then things should be fine.

Also, CDS_FULLSCREEN may have something to do with this but it's not implemented in Wine. It might affect how monitors get restored. I'll have to look into it.