In the "Search & Replace" window, if you switch tabs between "Search" and "Replace" you need an extra click to focus the first input field. (As opposed to open the window by either CTRL F or CTRL H: In this case the first input field has the focus)
It is a best UI practice to always focus the first form field.
Please add this behavior to remove also the inconsistency between directly invoking one of the tabs and switching tabs in the already opened window.