Regression, [WIN32SS] Scrolling by pressing the scrollbar arrows does not draw the arrows as pressed

Reproduction steps

• Open readme.txt from desktop with our notepad
• try to scroll the scrollbars by pressing the scroll arrows

Expected result

• I tested: When using our notepad.exe in Win XP and 2003SP2, the arrow-buttons will get into pressed state upon clicking

Observed result
0.4.13-RC-48-g818e5bc_buttonsNotPressed.webm
Ros does not log anything when it misbehaves like that, therefore I ommitted the log.

We can clearly deduce that the bug is not built into our notepad binary, but instead is deeper in ros. I would suspect a bug in win32ss/user/ntuser/scrollbar.c

Others confirmed my observation, therefore "accepted".
I wonder, whether it was always broken like that, or whether it regressed at some point?