WIP cost processing input cost are not fully accounted in output cost

Summary: Refer SR 3-37948697531

I have a work oder are complete partially. Cost profile using are as below

Cost Method: Perpetial average

Provisional Completions : Value using accumulated work in process balances

Provisional Completions for Process Manufacturing : Value using accumulated work in process balances

Operation Scrap Valuation : Value immediately and at work order close

Initial mass issue process complete and the WIP Balance is 0, on the last mass issue the input cost and output cost having variances, the variances has accounted in WIP Balance. The mass issue process we are completed at the same time, no backdated transaction. For the input cost partialy accounted into WIP Balance we suspect the cost processing for transfer cost from production to costing or create cost distribution process have issue and caused the WIP Balance and after work closed the WIP balance has goes into intentory write-off instead Cost of Goods Sales. The issue are not able