I open e.g. three windows of Okular with different documents. In my taskbar these get grouped into one entry "Okular" when there are to many applications on the desktop. Hoovering with the mouse over this entry gives me three previews of the Okular windows. Clicking on one of those entries does open not the entry that is corresponding to that preview. (Note: Although I used Okular in the example it can be reproduced with every application) Reproducible: Always Steps to Reproduce: 1. Configure Grouping to be active (right-click on the task-bar). Settings -> From the dropdown in grouping "Progamname" (I only have german locale). 2. Open some windows from one application (e.g. Dolphin or Okular) and make sure that these windows display different content. 3. Hoover on the taskbar - the preview appears - click on a window. Actual Results: Not the window associated to the preview appears. Expected Results: Window associated to the preview appears.
*** This bug has been marked as a duplicate of bug 365181 ***
Thank you for a solid bug report. Good news: Already fixed last week.