Credit balance in Deferred COGS

We have a credit balance in deferred cogs and in theory this should not happen.  As anyone else seen this?

1)  We did find a journal entry where it doubled up the transactions.  Why would this happen?  How do we get the detail of this transaction so we can make a correction?  In other words is there a report or is there a query I can use to get all the detail going to the deferred cogs account?

2)  We had some product we notice that the cost was at zero.  We since have updated the frozen cost.  Does the system at any point correct this error, ie move from inventory to cogs?  If not, like my previous question, how do I get to this data so I can make a journal entry?