Checked item script. Bunny Earplugs uses the same script as the following items for "bAtkRate":
-diabolous robes
-diabolous armoor
-+7 or higher ribbon hat/maiden hat
-and tons of battleground items
Of all those things, maiden hat is the oldest and first to use this script. I tried it myself on HP (I have the hat but I never looked at the Atk part since... it's not useful to me heh) and indeed the bAtkRate command is totally busted.
Add all of those items to the list of unfixables until svn update heh.
(GM can bypass this with the "old method" of how The Sign handled it: we can just say 3% bonus attack damage to all boss AND all non-boss types, and that'll *almost* be the same as 3% bonus attack. Unfortunately, this means that whitesmith and ninja and any other class with melee skills that don't work off % cards and demand direct +ATK will not benefit from the rabbit earplugs. However, that is the best and closest fix you can pull off in this svn.)