https://bugs.winehq.org/show_bug.cgi?id=56908
--- Comment #2 from Fabian Maurer dark.shadow4@web.de --- You can hack around the issue by 1) In show_scroll_bar comment out NtUserSetWindowPos 2) or making FlatSB_ShowScrollBar a no-op
It seems to do something to the scrollbars so that a redraw triggers a redraw, forever.