HI Gur,
It is unfortunately extremely difficult to answer a question like this, because COPA is individually built system. Each implementation is different.
It should typically have the following characteristics though:
1. Standard Cogs = the qty sold * with EITHER the SCE or VPRS.
2. Production variances from production, via the settlement process.
3. Overhead variances from the production cost centres, via assessment.
Many people incorrectly handle the CoGM vs the CoGS sold transaction incorrectly, especially the impact of the recovery from the income statement.
Unfortunately the best that I can do is to suggest you investigate the above flows and make sure that they are correct.
Regards
P