It was #24 in this thread but it seems that those images have been deleted. Not a problem, I took the time and made one for you. It's from a 4K display so you may need to download it for viewing.
There are two applications in view: Mozilla Thunderbird and Vivaldi (Chromium-based browser). Thunderbird starts with the main focus, then Vivaldi is clicked on. I click back to Thunderbird and wait a few seconds. Thunderbird then jumps in front of Vivaldi on its own.
This is a typical example of what is happening. Often times, Thunderbird, while not having focus, will jump behind the active application.
Notice that the tabs of one application are being aligned with the tabs of another. It's almost as if Groupy is mismatching the positional state of one application with another. You will also notice that the view in Thunderbird gets distorted. This is especially noticeable in the font rendering. In this example, a single monitor was used. When the windows jump across multiple displays, the distortion effect is very severe as the other display is 3440x1440 instead of 4K.
This is the issue that I have been reporting.