Huge Increase in Cost of Sales

After reading through previous posts on COGS and speaking to multiple NetSuite support representatives about this issue, I figured it was time for my first post to these forums to see if other users or someone from NetSuite can offer some insight. 

We have a situation where we sometimes go into negative inventory when inventory adjustments are done or incorrectly entered item receipts are changed.

The issue we are facing has to do with NetSuite's estimated "Cost of Sales" when inventory is negative. For the most part, NetSuite uses previous item receipts to come up with an estimated COGS, which is close to the true COGS. When items are received again and inventory becomes positive, the system posts a "cost of sales adjustment". We understand how this works and don't have a problem with it.