Alternate suggestion (somewhat alluded to by a previous response by Alan Kilborn):
Don’t move the vertical separator bar so that one of the views is fully obscured, leave at least one text line visible. The obscured pane is only hidden from the user, not from the editor. When a user makes the pane effectively invisible, what they are really doing is saying don’t show me the contents, so when the editor changes the contents (scrolls the file to display the match) the user can’t see what is going on.
This may not affect the purported bug, but it should at least make it easier to see what is going on. I do note that the Find All in All Opened Documents option will resize the document views to allow space for the Search results window and this may require appropriate resizing of all three panes.