Yesterday I upgraded from KDE 4.10.5 to KDE 4.11.2. Although most things are working fine, I'm experiencing a small inconvenience, seemingly a bug or broken configuration.

The task manager on the default panel is automatically grouping windows of the same type, even if "Only when taskbar is full" is enabled. For example, if there are no processes with windows open and I start two instances of Dolphin, they are automatically grouped, although there's plenty of space till the taskbar is full even in the slightest.

Someone else with 4.11 said they aren't getting this, so I assume it might be a broken configuration. Is anyone else getting the same problem in my version, and does anyone know what I can try to fix it?

I can confirm this, you should check bugs.kde.org and either confirm an existing bug or create a new one - probably caused by the rewrite of the widget to QML

Thank you for the confirmation. That means it's a bug in 4.11, and I reported it here.

fyi - I posted to the bug report and confirmed it is not fixed for 11.3, if you up to 11.3 you should also confirm it was not fixed as expected

update - seems my use of multiple rows is considered an edge case and does not demonstrate that it has not been fixed for 11.3, see comment #4 in the bug report