First, I am glad to hear that Toshiba is still providing brand-new players as warranty replacements (even though some like yours have the shutdown bug). Second, I recommend that you go ahead and install v4.0 firmware on your new player-it cannot hurt and may help. Let us know if it affects your shutdown problem.
(Actually, I should not say "it cannot hurt"... I bricked my shutting-down XA2 trying to install v3.0 a while back. The good news is, Toshiba replaced that player with yet another new one, which did not have the bug.)