Could you have edited or imported changes to the item? Most Recent Cost won't change on it's own. Something happened on the date in question for the 'Date of Change'.
In Adagio Inventory, you can selectively purge transactions from History, from the History report. Whatever gets printed to the report would be purged if you chose Yes to the question of purging. That could be receipts for a specific item within a certain date range, or whatever criteria is selected for the report.
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Regards,
Softrak Tech Support