Quick Launch bar, erroneously prevents the taskbar to get single-row again

Reproduction steps

• enable the QuickLaunchBar
• expand the taskbar by dragging to become a two-or-more-row-taskbar
• now try to make the taskbar single-row again

Expected result
in 2k3sp2 and XPSP3 this is trivial. Just drag the taskbar again, and voila: single-row again

Observed result
In ros it is impossible to get it back to single-row. No matter where you drag, be it at the taskbars edge (like one would expect). Be it on the QuickLaunch-toolbar-resize-sliders. Nope.
The only way to get it back to single-row is to disable the QuickLaunchBar beforehand.
0.4.15-dev-5137-g826bd41_HelpMe_wannaBeSingleRowAgain.webm
Nothing gets logged then, still here is:
0.4.15-dev-5137-g826bd41_HelpMe_wannaBeSingleRowAgain.log

Ftr: Currently if you had more than 2rows already, then dragging the taskbar back down will erroneously move the QuickLaunchbar-splitters also.