Hi Steve,

This is just postulation, but there was something addresed in a recent OE hot fix and it was in the current Service pack for 8.1E 2013.03.22; this is the very first in the 'problems fixed' list:

The Load History function on the Items tab in Display History displayed incorrect results in some cases when you had a range of
customers, items and dates, did a search, then changed fields in the range.

Perhaps the change to ensure that the correct results were loaded in some cases (such as a single item number) doesn't use the available indexes for fast searching in the most efficient manner.