Scrollbars THEMED drawing glitch in filebrowser treeview

Reproduction steps

• enable Lunar theme
• open C:\ReactOS\system32
• click in the menubar to open the folder-treeview on the left

Expected result
the scrollbars in that treeview should paint properly initially

Observed result
they do not draw properly until they are hovered over with the mouse pointer
This does not affect all scrollbars, only some special ones, like the mentioned ones
0.4.15-dev-3147-g3bf7e3a_affected.webm

the bug does not appear when ros is configured to use classic mode

might be related to CORE-17753 but I am not sure