The application Blitzin2 was sending WM_VSCROLL messages to the
richedit control directly, when normally this message is supposed to
be a notification sent after the scrollinfo is set.  Native richedit
controls always use the 16-bit value passed to this message to set the
scroll position for SB_THUMBPOSITION, rather than trying to find a
32-bit value through GetScrollInfo like I had previously done.