Under FileMaker Pro Advanced 14.0.2, when using the Script Debugger, if you single-step to a Pause/Resume Script [ Indefinitely ] step using the buttons at the top of the Debugger window, even if a field in the supposedly active normal FileMaker window has a blinking cursor and a highlighted perimeter, typing to enter a value will not work, and a "beep" occurs.
I don't think this was the behavior of the script debugger in prior versions. Apparently the Script Debugger is considered the actual active window even though the script has been working on the normal window... so you can't actually enter any values into a field unless you click on the normal window (title bar, for example) to make the presumed active window able to accept input.
Note that using the F5, F6, F7 keys, etc. for stepping avoids this problem.
It seems like the floating-window nature of the Script Debugger shouldn't be intercepting any keystrokes.