Quick Launch bar and taskbar buttons do intertwine erroneously, taskbar-goulash

Reproduction steps

• empty all elements in the QuickLaunchBar (QLB)
• enable the QuickLaunchBar
• set the taskbar to "unfixed" so that QLBs resize-sliders become visible
• open some arbitrary app to create an open taskbar-button / taskbar-pane
• now move the QuickLaunchBar right resize-slider to the right side to enlarge the QLB

Expected result
on 2k3sp2 and XPSP3 the taskbar-panes would automatically be moved to the right when the QLB gets enlarged like that. They would never intertwine or overlap with the QLB.

Observed result
On ros both will intertwine in a fancy way. Taskbar-goulash is the result
0.4.15-dev-5137-g826bd41_intertwine.webm
Nothing gets logged uppon goulashing, still here is 0.4.15-dev-5137-g826bd41_intertwine.log