I just got the 202112071438 version. The issue has been "fixed" but it's still inconsistent and sometimes buggy. The text which is the title of the preview is not always on the same position, and when reshaping a windows outside of Jami, the thumbnail can get outside of the borders again, with the text don't displaying anymore. Only after clicking on the field of the thumbnail in Jami, the thumbnail resizes correctly again.
It seems that our computer is not very powerful as the preview updates are sluggish as you can see Screen 0 and Screen 1 are black, yet All Screens shows both screens.
Could the captions for the Screens (i.e. Screen 0, Screen 1, and All Screens) and Windows for each thumbnail be at the top (instead of the bottom) (see image above with the red arrows) so that it will always be positioned at the same place in the thumbnail?