Epic armor/shield enhancements not getting masterwork reduction to armor check penalty

For some reason, a shield or armor of +1 to +5 bonus is getting the 1 point reduction to their armor check penalty expected of masterwork items, but a shield or armor with bonuses of +6 to +10 are not.

(I've tried it with the latest autobuild and data from an updated SVN, so the previous fix regarding non-stacking of epic-level shield and armor enhancements hasn't fixed this issue.)