At the end of December 2019, I condensed a company file that was started in 2006
So it had 13 years of data and was very large
All items, Customers, Vendors were kept
Only all the transactions were eliminated in the condense

So now I see a huge problem with items average cost because it showed up in the P&L report for January
Way back in 2006 when Quickbooks was originally set up, the on hand quantities were not entered correctly for all the items. 
This never showed up on the P & L as a problem prior to 2020
But now, that all transactions are gone I am seeing items that cost $0.20 showing and average cost of $29.28.
This item is sold by the foot and a lot of this items is sold every day
This is causing a huge issue in this months P&L because the average cost of $29 is showing a loss on every sales receipt.
The items are always paid for with the correct cost in the Write Checks section of QB
The invoice amount has to match the check amount.
So purchasing items has never been the problem.
The quantities and cost are always entered correctly when paying vendors
But, the on hand quantities being sold are very negative on many items

After reading lots of info about this Average Cost issue here, I see no way to correct the average cost.
What I did as a test is change the name of the item and then add a new item with the original name, the cost and the correct on hand.
Name changed from Cable to Cable_old
New item set up as Cable and this item will be sold from now on
Now this new item shows the correct average cost as $0.20 and it is coming up correctly in sales receipts.

I can't wait around for these items to get transactions and hope the average cost gets fixed
Can anyone tell my why this is not something I should do?

Here's some screen shots
Screen shot of Sales receipt with the Cable_old and New Cable sold with qty one each
Screen shot of old and new item
Screen shot of Transaction detail showing wrong Average cost of $29.29 on old item
And showing correct average cost on new item