OK, just noticed this bug..
T'was available in 4.0 and now still in 4.02:
command <t.d> msg <$t.menu(text;start;red)$>
Comand that calls a function:
define function <t.menu>
enter <t.menu.choice>
return <#t.menu.choice#>
end define
Run the command, then close Quest.
You'll see it hanging in the background - although the window is not showing.
You can also try the program menu:
Quest->Restart Game
This time it crashes the game, as "an array is fixed/temporarily locked".