Wrong size of taskbar thumbnail at first show

[utnaishtim]

Hello,

With Windows 10 v1803 and later, the taskbar thumbnails don't show up with the good ratio width/height. They are fine after the second show.

The enclosed archive contains a Visual Studio 2019 project that exhibits the problem: it generates a new thumbnail every 10 seconds. When hovering on the taskbar, the thumbnail doesn't have the expected square aspect. When leaving the taskbar and coming back, the thumbnail now has the good aspect.
You can then wait 10 seconds to invalidate the thumbnail and see the problem again.

Thumbnail.zip