Actual Variance for MUV

We have created several work orders, and when we finished them and move them to status 99, we get high MUV, from planned vs actual in all the fields - material, hours and overhead, and the completed quantities are ok, so the variance is not coming from what was issue from inventories, the BOM cost is set per standar and per branch plant, the item cost is set to take cost per branch plant, any ideas where i can look for this high MUV since all the super back flush operations were completed as supposed to. But we are getting