Effects of changing Profit/Price Calculation

An Item using FIFO was created (in late 2012) with Profit/Price Calc : Profit = Price-Cost, during which time a Sale Item Ledger Entry was posted with 0 Cost and Price, hence no G/L entries

Later (in 2013) after corrected the calc to be Price = Profit + Cost, another Sale Type Item Ledger Entry was posted, but this time with correct item Cost and Price.

I thought the Profit/price Calc helps determine the Profit % or Unit Price, in either case, both Unit Cost and Price of the Item always be the same.

What is causing the 0 amount posting to the Item Ledger? Most important of all, what would be the best way to fix the interim difference?

The Price/Profit calculation has no impact on costing and shoud be used for informational purposes as it just affects the Unit Price in the Item Card, not the sales prices in the price items.

NAV in general uses the costs published to the item journal for positive entries (purchase and pos. adj.) to value the stock.
Based on FIFO, the system takes those costs for neg. entries (ie sales and neg. adjustments).
The Sales amounts and therefore the profit is determined by the price you enter on the sales entries.

This all applies when you manually post the item transactions using the item journal directly.
Usually the values (costs and sales amounts) are determined by the Sales Invoices and Purchase Invoices automatically.

To correct the zero cost values of positive and negative transactions can be corrected using the revaluation journal.
Zero Sales amounts cannot be corrected this way.