Multiple receipts on one purchase order line causes faulty Average PO calculation due to error in cost detail

Steps how to reproduce the error:
1. Create a product with purchase price 100.
2. Create and complete a purchase order for 10 units of the product.
3. Create and complete a material receipt for that order with 5 units. Use "create from order".
4. Create and complete one more material receipt for that order with 5 units. Use "Create from order".
5. Create and complete a purchase order for 5 units of the product. Change purchase price to 150.
6. Create and complete a material reciept for that order with 5 units. Use "create from order"
7. Create and complete a vendor invoice for all 15 units. Use create from order.
8. Run Client Accounting Processor
9. Match PO-Receipt-Invoice Invoice -> Receipt.
10. Run client accounting processor

NOTE!! This error seems to turn out different depending on when the accounting processor is run. If the accounting processor is run between each step the result is different than if it's run only in the end.

Errors:
1. Because of step 4 a faulty Cost Detail Record is created when accounting processor is run last. Qty is set to 10 instead of 5.
2. Step 7 doesn't automatically match the invoice line to the first receipt line created in step 4. Only the last receipt is matched. Manual matching is required. See IDEMPIERE-514.
3. Error 1 causes Average PO to be wrongly calculated.
4. Standard costing doesn't look right either.

Alternatives:

• If accounting processor is run between each step, Average Invoice turns out wrong and average PO will be correct. Match PO-Receipt-Invoice Purchase Order -> Receipt will show unmatched PO-line even though it's matched.

• If accounting processor is run between steps 6 and 7 everything turns out correct.

A clue to the problem might be that when the accounting processor is run between each step a purchase order cost detail record is created for each receipt but when the accounting processor is run last one receipt is counted twice.