FM Closes Wrong Window
I've been having this issue only in Windows, while under Mac there is no problem.
When there are several windows open, clicking X (close) button on a background (unselected) window closes the foreground (selected) window.
I tried creating a custom menu function where X corresponds to a script step of Select Window (Current), Close Window(Current), however that did not solve the problem.
This happens whether one database is open or several at the same time. Whichever unselected windows X is pressed, the selected window closes.