Dear Maintainer,

   * What led up to the situation?
I am using Debian stable with the actual version of Mate desktop.

   * What exactly did you do (or not do) that was effective (or
     ineffective)?
Running an arbitrary application (Firefox) that has a running window entry on
the bottom panel (in the Window List), and pointing on it with a mouse so it
shows a thumbnail of the window content.

   * What was the outcome of this action?
The thumbnail/preview contained an outdated window content. It seems that this
thumbnail is generated just once and it is not refreshed later.

   * What outcome did you expect instead?
The thumbnail/preview should be refreshed each time before it is displayed.