Why does deferred COGS have a balance and how to clear it

we have a issue where deferred cogs shows a balance for a part whose selling price is 0.we have run the necessary programs like collect revenue recognition , generate cogs recognition events etc .Another part on the same sales order has the deferred cogs cleared but this part has non zero selling price.

If the selling price is zero , will the deferred cogs alwyas have a balance?do we have to pass a manual journal entry to clear it?

Thanks

Rahul