SUMMARY
When multiple instances of a program in the icon-only task manager are opened and grouped, they can not be cycled through on click when all instances are minimized or another program is in focus. Mouse wheel does work.

STEPS TO REPRODUCE
1. Open multiple instances with icon only task manager and grouping
2. Minimize all instances or switch to another program
3. Click on icon in task manager

OBSERVED RESULT
Nothing happens (see journal output under additional information section)

EXPECTED RESULT
Instances should open one after another

SOFTWARE/OS VERSIONS
Operating System: openSUSE Tumbleweed 20210429
KDE Plasma Version: 5.21.4
KDE Frameworks Version: 5.81.0
Qt Version: 5.15.2
Kernel Version: 5.12.0-1-default
OS Type: 64-bit
Graphics Platform: Wayland

ADDITIONAL INFORMATION
Journal shows following output:

Mai 02 11:41:48 saturn plasmashell[3837]: need a window and a context QQuickWindow(0)
Mai 02 11:42:15 saturn plasmashell[3837]: "Could not convert argument 0 at"
Mai 02 11:42:15 saturn plasmashell[3837]:          "activateTask@file:///usr/share/plasma/plasmoids/org.kde.plasma.taskmanager/contents/ui/code/to>
Mai 02 11:42:15 saturn plasmashell[3837]:          "onReleased@file:///usr/share/plasma/plasmoids/org.kde.plasma.taskmanager/contents/ui/Task.qml:>
Mai 02 11:42:15 saturn plasmashell[3837]: "Passing incompatible arguments to C++ functions from JavaScript is dangerous and deprecated."
Mai 02 11:42:15 saturn plasmashell[3837]: "This will throw a JavaScript TypeError in future releases of Qt!"