Uninstaller of MS .NET 4.0 draws an unintended vertical scrollbar that partly disappears upon mouse scrollwheel scrolling

The ticket heavily reminds me of CORE-15429, still I create a fresh ticket, to be able to crosstest that with a ros-independant third-party-app against Wine.

Microsoft .NET Framework 4.0 from rapps.

Reproduction steps
-install .NET 4.0
-run the uninstall of .NET 4.0 Client profile or alternatively Extended profile
-A warning dlg will show up (just telling you that .NET apps will not longer run when uninstalling .NET)
-I think it's a RichEdit where that warning is displayed (is that correct?)

Expected result
That RichEdit should not have any vertical scrollbar
like xpsp3.webm

Observed result
-In ros 0.4.11-RC-36-gc5204e3 gcc dbg linux it displays a vertical scrollbar erroneously
-As soon as we scroll with the scrollwheel, the scrollbar partially disappears
-when we drag the window offscreen and back aftewrwards, that vertical scrollbar fully disappears
0.4.11-RC-36-gc5204e3_NET4_0_uninstall.webm
0.4.11-RC-36-gc5204e3_NET4_0_uninstall.log
That issue is perfectly reproducible for me when I start the uninstaller several times one after another.