This happens in a very specific situation - when the user has multiple displays which get disconnected except one, but the one that does not get disconnected has its menu block closed - in this case this sole display will appear without a header by default, however the Tools menu header thinks the display's menu block above it is still closed and formats the header corners accordingly.
This happens in a very specific situation - when the user has multiple displays which get disconnected except one, but the one that does not get disconnected has its menu block closed - in this case this sole display will appear without a header by default, however the Tools menu header thinks the display's menu block above it is still closed and formats the header corners accordingly.