Inventory journal entries not balanced since error is made before validation

Hi,
My customer has a probme with inventory journal entries.

Consider you enter a transaction with P4112 for an item.
for the line, enter 10 for the qty. suppose the cost is =1.
use sub ledger type = C and enter a wrong cost center. The systme display an error.
re-enter another wrong cost center. the system display an error.
then enter a valid cost centrer and .

after validating the transaction, the journal entries created are as follow :

amount = 3 x 10 for the inventory account
amount = 10 for the variance.

then  the journal line is not balanced.

Do you have any idea to resolve this problem ?