We use QBDE's average costing for valuing Inventories and COGS. I have a small team that uses our company file for ordering and shipping items.  At each month end, I enter Quantity Adjustments to our on hand inventories. I ran some prior period reports and noticed my COGS and Inventory values had changed in periods that had been closed for several months. 

I was able to track down the change in Inventory Valuation by Item using old backup files to compare against my live file.  For some reason, a group of FG parts that historically had Avg Cost = $0.01 now suddenly have an Avg Cost value = $0.27.  I cannot determine what caused the change in Avg Cost nor why the change went retroactive and changed financials in closed periods. 

Can anyone help me correct the live file so my financials are back to pre-change amounts?